diff --git a/config/config.go b/config/config.go
index ccefd7f46..c6f5677d4 100644
--- a/config/config.go
+++ b/config/config.go
@@ -2,12 +2,10 @@ package config
 
 import (
 	"errors"
-	"fmt"
 	"reflect"
 	"sync"
 	"time"
 
-	"github.com/go-kratos/kratos/v2/encoding"
 	"github.com/go-kratos/kratos/v2/log"
 
 	// init encoding
@@ -50,17 +48,9 @@ type config struct {
 // New new a config with options.
 func New(opts ...Option) Config {
 	options := options{
-		logger: log.DefaultLogger,
-		decoder: func(src *KeyValue, target map[string]interface{}) error {
-			if src.Format == "" {
-				target[src.Key] = src.Value
-				return nil
-			}
-			if codec := encoding.GetCodec(src.Format); codec != nil {
-				return codec.Unmarshal(src.Value, &target)
-			}
-			return fmt.Errorf("unsupported key: %s format: %s", src.Key, src.Format)
-		},
+		logger:   log.DefaultLogger,
+		decoder:  defaultDecoder,
+		resolver: defaultResolver,
 	}
 	for _, o := range opts {
 		o(&options)
diff --git a/config/config_test.go b/config/config_test.go
new file mode 100644
index 000000000..f9bb5a7b7
--- /dev/null
+++ b/config/config_test.go
@@ -0,0 +1,141 @@
+package config
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDefaultResolver(t *testing.T) {
+	var (
+		portString = "8080"
+		countInt   = 10
+		enableBool = true
+		rateFloat  = 0.9
+	)
+
+	data := map[string]interface{}{
+		"foo": map[string]interface{}{
+			"bar": map[string]interface{}{
+				"notexist": "${NOTEXIST:100}",
+				"port":     "${PORT:8081}",
+				"count":    "${COUNT:0}",
+				"enable":   "${ENABLE:false}",
+				"rate":     "${RATE}",
+				"empty":    "${EMPTY:foobar}",
+				"array":    []interface{}{"${PORT}", "${NOTEXIST:8081}"},
+				"value1":   "${test.value}",
+				"value2":   "$PORT",
+				"value3":   "$PORT:default",
+			},
+		},
+		"test": map[string]interface{}{
+			"value": "foobar",
+		},
+		"PORT":   "8080",
+		"COUNT":  "10",
+		"ENABLE": "true",
+		"RATE":   "0.9",
+		"EMPTY":  "",
+	}
+
+	tests := []struct {
+		name   string
+		path   string
+		expect interface{}
+	}{
+		{
+			name:   "test not exist int env with default",
+			path:   "foo.bar.notexist",
+			expect: 100,
+		},
+		{
+			name:   "test string with default",
+			path:   "foo.bar.port",
+			expect: portString,
+		},
+		{
+			name:   "test int with default",
+			path:   "foo.bar.count",
+			expect: countInt,
+		},
+		{
+			name:   "test bool with default",
+			path:   "foo.bar.enable",
+			expect: enableBool,
+		},
+		{
+			name:   "test float without default",
+			path:   "foo.bar.rate",
+			expect: rateFloat,
+		},
+		{
+			name:   "test empty value with default",
+			path:   "foo.bar.empty",
+			expect: "",
+		},
+		{
+			name:   "test array",
+			path:   "foo.bar.array",
+			expect: []interface{}{portString, "8081"},
+		},
+		{
+			name:   "test ${test.value}",
+			path:   "foo.bar.value1",
+			expect: "foobar",
+		},
+		{
+			name:   "test $value",
+			path:   "foo.bar.value2",
+			expect: portString,
+		},
+		{
+			name:   "test $value:default",
+			path:   "foo.bar.value3",
+			expect: portString + ":default",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			err := defaultResolver(data)
+			assert.NoError(t, err)
+			rd := reader{
+				values: data,
+			}
+			if v, ok := rd.Value(test.path); ok {
+				var actual interface{}
+				switch test.expect.(type) {
+				case int:
+					if actual, err = v.Int(); err == nil {
+						assert.Equal(t, test.expect, int(actual.(int64)), "int value should be equal")
+					}
+				case string:
+					if actual, err = v.String(); err == nil {
+						assert.Equal(t, test.expect, actual, "string value should be equal")
+					}
+				case bool:
+					if actual, err = v.Bool(); err == nil {
+						assert.Equal(t, test.expect, actual, "bool value should be equal")
+					}
+				case float64:
+					if actual, err = v.Float(); err == nil {
+						assert.Equal(t, test.expect, actual, "float64 value should be equal")
+					}
+				default:
+					actual = v.Load()
+					if !reflect.DeepEqual(test.expect, actual) {
+						t.Logf("expect: %#v, actural: %#v", test.expect, actual)
+						t.Fail()
+					}
+				}
+				if err != nil {
+					t.Error(err)
+				}
+			} else {
+				t.Error("value path not found")
+			}
+		})
+	}
+}
diff --git a/config/options.go b/config/options.go
index 5bc9ebf0b..278698b34 100644
--- a/config/options.go
+++ b/config/options.go
@@ -1,19 +1,28 @@
 package config
 
 import (
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/go-kratos/kratos/v2/encoding"
 	"github.com/go-kratos/kratos/v2/log"
 )
 
 // Decoder is config decoder.
 type Decoder func(*KeyValue, map[string]interface{}) error
 
+// Resolver resolve placeholder in config.
+type Resolver func(map[string]interface{}) error
+
 // Option is config option.
 type Option func(*options)
 
 type options struct {
-	sources []Source
-	decoder Decoder
-	logger  log.Logger
+	sources  []Source
+	decoder  Decoder
+	resolver Resolver
+	logger   log.Logger
 }
 
 // WithSource with config source.
@@ -30,9 +39,67 @@ func WithDecoder(d Decoder) Option {
 	}
 }
 
+// WithResolver with config resolver.
+func WithResolver(r Resolver) Option {
+	return func(o *options) {
+		o.resolver = r
+	}
+}
+
 // WithLogger with config logger.
 func WithLogger(l log.Logger) Option {
 	return func(o *options) {
 		o.logger = l
 	}
 }
+
+// defaultDecoder decode config from source KeyValue
+// to target map[string]interface{} using src.Format codec.
+func defaultDecoder(src *KeyValue, target map[string]interface{}) error {
+	if src.Format == "" {
+		target[src.Key] = src.Value
+		return nil
+	}
+	if codec := encoding.GetCodec(src.Format); codec != nil {
+		return codec.Unmarshal(src.Value, &target)
+	}
+	return fmt.Errorf("unsupported key: %s format: %s", src.Key, src.Format)
+}
+
+// defaultResolver resolve placeholder in map value,
+// placeholder format in ${key:default} or $key.
+func defaultResolver(input map[string]interface{}) error {
+	mapper := func(name string) string {
+		args := strings.Split(strings.TrimSpace(name), ":")
+		if v, has := readValue(input, args[0]); has {
+			s, _ := v.String()
+			return s
+		} else if len(args) > 1 { // default value
+			return args[1]
+		}
+		return ""
+	}
+
+	var resolve func(map[string]interface{}) error
+	resolve = func(sub map[string]interface{}) error {
+		for k, v := range sub {
+			switch vt := v.(type) {
+			case string:
+				sub[k] = os.Expand(vt, mapper)
+			case map[string]interface{}:
+				if err := resolve(vt); err != nil {
+					return err
+				}
+			case []interface{}:
+				for i, iface := range vt {
+					if s, ok := iface.(string); ok {
+						vt[i] = os.Expand(s, mapper)
+					}
+				}
+				sub[k] = vt
+			}
+		}
+		return nil
+	}
+	return resolve(input)
+}
diff --git a/config/reader.go b/config/reader.go
index 71806a3ca..2dc778c3e 100644
--- a/config/reader.go
+++ b/config/reader.go
@@ -43,6 +43,9 @@ func (r *reader) Merge(kvs ...*KeyValue) error {
 			return err
 		}
 	}
+	if err := r.opts.resolver(merged); err != nil {
+		return err
+	}
 	r.values = merged
 	return nil
 }
diff --git a/config/reader_test.go b/config/reader_test.go
index d7c3d179b..2cec467af 100644
--- a/config/reader_test.go
+++ b/config/reader_test.go
@@ -20,6 +20,7 @@ func TestReader_Merge(t *testing.T) {
 			}
 			return fmt.Errorf("unsupported key: %s format: %s", kv.Key, kv.Format)
 		},
+		resolver: defaultResolver,
 	}
 	r := newReader(opts)
 	err = r.Merge(&KeyValue{
@@ -55,10 +56,6 @@ func TestReader_Merge(t *testing.T) {
 }
 
 func TestReader_Value(t *testing.T) {
-	var (
-		err error
-		ok  bool
-	)
 	opts := options{
 		decoder: func(kv *KeyValue, v map[string]interface{}) error {
 			if codec := encoding.GetCodec(kv.Format); codec != nil {
@@ -66,42 +63,73 @@ func TestReader_Value(t *testing.T) {
 			}
 			return fmt.Errorf("unsupported key: %s format: %s", kv.Key, kv.Format)
 		},
+		resolver: defaultResolver,
 	}
-	r := newReader(opts)
-	err = r.Merge(&KeyValue{
-		Key:    "b",
-		Value:  []byte(`{"a": {"b": {"X": 1, "Y": "lol", "z": true}}}`),
-		Format: "json",
-	})
-	assert.NoError(t, err)
-	vv, ok := r.Value("a.b.X")
-	assert.True(t, ok)
-	vvv, err := vv.Int()
-	assert.NoError(t, err)
-	assert.Equal(t, int64(1), vvv)
 
-	assert.NoError(t, err)
-	vv, ok = r.Value("a.b.Y")
-	assert.True(t, ok)
-	vvy, err := vv.String()
-	assert.NoError(t, err)
-	assert.Equal(t, "lol", vvy)
+	ymlval := `
+a: 
+  b: 
+    X: 1
+    Y: "lol"
+    z: true
+`
+	tests := []struct {
+		name string
+		kv   KeyValue
+	}{
+		{
+			name: "json value",
+			kv: KeyValue{
+				Key:    "config",
+				Value:  []byte(`{"a": {"b": {"X": 1, "Y": "lol", "z": true}}}`),
+				Format: "json",
+			},
+		},
+		{
+			name: "yaml value",
+			kv: KeyValue{
+				Key:    "config",
+				Value:  []byte(ymlval),
+				Format: "yaml",
+			},
+		},
+	}
 
-	assert.NoError(t, err)
-	vv, ok = r.Value("a.b.z")
-	assert.True(t, ok)
-	vvz, err := vv.Bool()
-	assert.NoError(t, err)
-	assert.Equal(t, true, vvz)
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			r := newReader(opts)
+			err := r.Merge(&test.kv)
+			assert.NoError(t, err)
+			vv, ok := r.Value("a.b.X")
+			assert.True(t, ok)
+			vvv, err := vv.Int()
+			assert.NoError(t, err)
+			assert.Equal(t, int64(1), vvv)
 
-	vv, ok = r.Value("aasasdg=234l.asdfk,")
-	assert.False(t, ok)
+			assert.NoError(t, err)
+			vv, ok = r.Value("a.b.Y")
+			assert.True(t, ok)
+			vvy, err := vv.String()
+			assert.NoError(t, err)
+			assert.Equal(t, "lol", vvy)
 
-	vv, ok = r.Value("aas......asdg=234l.asdfk,")
-	assert.False(t, ok)
+			assert.NoError(t, err)
+			vv, ok = r.Value("a.b.z")
+			assert.True(t, ok)
+			vvz, err := vv.Bool()
+			assert.NoError(t, err)
+			assert.Equal(t, true, vvz)
 
-	vv, ok = r.Value("a.b.Y.")
-	assert.False(t, ok)
+			vv, ok = r.Value("aasasdg=234l.asdfk,")
+			assert.False(t, ok)
+
+			vv, ok = r.Value("aas......asdg=234l.asdfk,")
+			assert.False(t, ok)
+
+			vv, ok = r.Value("a.b.Y.")
+			assert.False(t, ok)
+		})
+	}
 }
 
 func TestReader_Source(t *testing.T) {
@@ -115,6 +143,7 @@ func TestReader_Source(t *testing.T) {
 			}
 			return fmt.Errorf("unsupported key: %s format: %s", kv.Key, kv.Format)
 		},
+		resolver: defaultResolver,
 	}
 	r := newReader(opts)
 	err = r.Merge(&KeyValue{