diff --git a/docs/installation_guide.md b/docs/installation_guide.md
index 59f98bda5..7dcacc1ef 100644
--- a/docs/installation_guide.md
+++ b/docs/installation_guide.md
@@ -344,6 +344,10 @@ hostname = 192.168.0.2:8888
 
 4.Re-deploy Harbor referring to previous section "Managing Harbor's lifecycle".
 
+## Configuring Harbor using the external database
+Currently, only PostgreSQL database is supported by Harbor.  
+To user an external database, just uncomment the `external_database` section in `harbor.yml` and fill the necessary information. Four databases are needed to be create first by users for Harbor core, Clair, Notary server and Notary signer. And the tables will be generated automatically when Harbor starting up.  
+
 ## Manage user settings
 After release 1.8.0, User settings are separated with system settings, and all user settings should be configured in web console or by HTTP request.
 Please refer [Configure User Settings](configure_user_settings.md) to config user settings.
diff --git a/make/harbor.yml b/make/harbor.yml
index 47718929d..3d41187b4 100644
--- a/make/harbor.yml
+++ b/make/harbor.yml
@@ -80,8 +80,9 @@ log:
 #This attribute is for migrator to detect the version of the .cfg file, DO NOT MODIFY!
 _version: 1.8.0
 
-# Uncomment external_database if using external database.
-# Currently only support POSTGRES, the password will replace the password setting in database.
+# Uncomment external_database if using external database. Currently only support POSTGRES. 
+# Four databases are needed to be create first by users for Harbor core, Clair, Notary server 
+# and Notary signer. And the tables will be generated automatically when Harbor starting up.
 # NOTE: external_database is unable to custom attributes individually, you must do them in block.
 # external_database:
 #   harbor: