diff --git a/metadata/identifier/base_metadata_identifier.go b/metadata/identifier/base_metadata_identifier.go
index a314671055..5f3df4c607 100644
--- a/metadata/identifier/base_metadata_identifier.go
+++ b/metadata/identifier/base_metadata_identifier.go
@@ -25,11 +25,13 @@ import (
 	"github.com/apache/dubbo-go/common/constant"
 )
 
+// BaseMetadataIdentifier defined for description the Metadata base identify
 type BaseMetadataIdentifier interface {
 	getFilePathKey(params ...string) string
 	getIdentifierKey(params ...string) string
 }
 
+// BaseMetadataIdentifier is the base implement of BaseMetadataIdentifier interface
 type BaseServiceMetadataIdentifier struct {
 	serviceInterface string
 	version          string
@@ -37,7 +39,7 @@ type BaseServiceMetadataIdentifier struct {
 	side             string
 }
 
-// joinParams...
+// joinParams will join the specified char in slice, and return a string
 func joinParams(joinChar string, params []string) string {
 	var joinedStr string
 	for _, param := range params {
@@ -47,7 +49,7 @@ func joinParams(joinChar string, params []string) string {
 	return joinedStr
 }
 
-// getIdentifierKey...
+// getIdentifierKey returns string that format is service:Version:Group:Side:param1:param2...
 func (mdi *BaseServiceMetadataIdentifier) getIdentifierKey(params ...string) string {
 	return mdi.serviceInterface +
 		constant.KEY_SEPARATOR + mdi.version +
@@ -56,7 +58,7 @@ func (mdi *BaseServiceMetadataIdentifier) getIdentifierKey(params ...string) str
 		joinParams(constant.KEY_SEPARATOR, params)
 }
 
-// getFilePathKey...
+// getFilePathKey returns string that format is metadata/path/Version/Group/Side/param1/param2...
 func (mdi *BaseServiceMetadataIdentifier) getFilePathKey(params ...string) string {
 	path := serviceToPath(mdi.serviceInterface)
 
@@ -69,7 +71,6 @@ func (mdi *BaseServiceMetadataIdentifier) getFilePathKey(params ...string) strin
 
 }
 
-// serviceToPath...
 func serviceToPath(serviceInterface string) string {
 	if serviceInterface == constant.ANY_VALUE {
 		return ""
@@ -83,7 +84,6 @@ func serviceToPath(serviceInterface string) string {
 
 }
 
-//withPathSeparator...
 func withPathSeparator(path string) string {
 	if len(path) != 0 {
 		path = constant.PATH_SEPARATOR + path
diff --git a/metadata/identifier/metadata_identifier.go b/metadata/identifier/metadata_identifier.go
index f3df8f3654..7e72c10da9 100644
--- a/metadata/identifier/metadata_identifier.go
+++ b/metadata/identifier/metadata_identifier.go
@@ -17,17 +17,18 @@
 
 package identifier
 
+// MetadataIdentifier is inherit baseMetaIdentifier with Application name
 type MetadataIdentifier struct {
 	application string
 	BaseMetadataIdentifier
 }
 
-// getIdentifierKey...
+// GetIdentifierKey returns string that format is service:Version:Group:Side:Application
 func (mdi *MetadataIdentifier) getIdentifierKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getIdentifierKey(mdi.application)
 }
 
-// getIdentifierKey...
+// GetFilePathKey returns string that format is metadata/path/Version/Group/Side/Application
 func (mdi *MetadataIdentifier) getFilePathKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getFilePathKey(mdi.application)
 }
diff --git a/metadata/identifier/service_metadata_identifier.go b/metadata/identifier/service_metadata_identifier.go
index 373df0130d..ccc149f730 100644
--- a/metadata/identifier/service_metadata_identifier.go
+++ b/metadata/identifier/service_metadata_identifier.go
@@ -21,18 +21,19 @@ import (
 	"github.com/apache/dubbo-go/common/constant"
 )
 
+// ServiceMetadataIdentifier is inherit baseMetaIdentifier with service params: Revision and Protocol
 type ServiceMetadataIdentifier struct {
 	revision string
 	protocol string
 	BaseMetadataIdentifier
 }
 
-// getIdentifierKey...
+// GetIdentifierKey returns string that format is service:Version:Group:Side:Protocol:"revision"+Revision
 func (mdi *ServiceMetadataIdentifier) getIdentifierKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getIdentifierKey(mdi.protocol + constant.KEY_REVISON_PREFIX + mdi.revision)
 }
 
-// getIdentifierKey...
+// GetFilePathKey returns string that format is metadata/path/Version/Group/Side/Protocol/"revision"+Revision
 func (mdi *ServiceMetadataIdentifier) getFilePathKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getFilePathKey(mdi.protocol + constant.KEY_REVISON_PREFIX + mdi.revision)
 }
diff --git a/metadata/identifier/subscribe_metadata_identifier.go b/metadata/identifier/subscribe_metadata_identifier.go
index 321a216a3e..38f3ebbd46 100644
--- a/metadata/identifier/subscribe_metadata_identifier.go
+++ b/metadata/identifier/subscribe_metadata_identifier.go
@@ -17,17 +17,18 @@
 
 package identifier
 
+// SubscriberMetadataIdentifier is inherit baseMetaIdentifier with service params: Revision
 type SubscriberMetadataIdentifier struct {
 	revision string
 	BaseMetadataIdentifier
 }
 
-// getIdentifierKey...
+// GetIdentifierKey returns string that format is service:Version:Group:Side:Revision
 func (mdi *SubscriberMetadataIdentifier) getIdentifierKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getIdentifierKey(mdi.revision)
 }
 
-// getIdentifierKey...
+// GetFilePathKey returns string that format is metadata/path/Version/Group/Side/Revision
 func (mdi *SubscriberMetadataIdentifier) getFilePathKey(params ...string) string {
 	return mdi.BaseMetadataIdentifier.getFilePathKey(mdi.revision)
 }
diff --git a/metadata/service.go b/metadata/service.go
index d85703c95a..89df68fb31 100644
--- a/metadata/service.go
+++ b/metadata/service.go
@@ -22,6 +22,9 @@ import (
 	gxset "github.com/dubbogo/gost/container/set"
 )
 
+// Metadata service is a built-in service around the metadata of Dubbo services,
+// whose interface is provided by Dubbo Framework and exported automatically before subscription after other services exporting,
+// which may be used for Dubbo subscribers and admin.
 type MetadataService interface {
 	ServiceName() string
 	ExportURL(url *common.URL) bool