diff --git a/lib/dingtalk/api/base.rb b/lib/dingtalk/api/base.rb
index 6241f79..6404c23 100644
--- a/lib/dingtalk/api/base.rb
+++ b/lib/dingtalk/api/base.rb
@@ -2,19 +2,32 @@ module Dingtalk
   module Api
     class Base
       attr_accessor :corp_id
+      ACCESS_TOKEN = "access_token"
 
       def initialize(corp_id = nil)
         @corp_id = corp_id
       end
 
+      def access_token
+        "#{corp_id}_#{ACCESS_TOKEN}"
+      end
+
       private
+        def default_params
+          { access_token: access_token }
+        end
+
+        def payload(params = {})
+          [ request_url(url), default_params.merge(params).to_json, { content_type: :json } ]
+        end
+
         def http_get(url, params = {})
-          res = RestClient.get(request_url(url), params.to_json, content_type: :json)
+          res = RestClient.get(payload(params))
           JSON.parse(res)
         end
 
         def http_post(url, params = {})
-          res = RestClient.post(request_url(url), params.to_json, content_type: :json)
+          res = RestClient.post(payload(params))
           JSON.parse(res)
         end
 
diff --git a/lib/dingtalk/api/department.rb b/lib/dingtalk/api/department.rb
new file mode 100644
index 0000000..2ddd259
--- /dev/null
+++ b/lib/dingtalk/api/department.rb
@@ -0,0 +1,14 @@
+module Dingtalk
+  module Api
+    class Department < Base
+      def list
+        http_get('list')
+      end
+
+      private
+        def base_url
+          'department'
+        end
+    end
+  end
+end
diff --git a/lib/dingtalk/api/suite.rb b/lib/dingtalk/api/suite.rb
index 609c227..4521f95 100644
--- a/lib/dingtalk/api/suite.rb
+++ b/lib/dingtalk/api/suite.rb
@@ -29,7 +29,7 @@ module Dingtalk
           suite_secret: @suite_secret,
           suite_ticket: suite_ticket
         }
-        http_post(request_url('get_suite_token'), params)
+        http_post('get_suite_token', params)
         # TODO check response values
         redis.set(SUITE_ACCESS_TOKEN, res['suite_access_token'])
         redis.expire(SUITE_ACCESS_TOKEN, EXPIRATION)
@@ -41,6 +41,10 @@ module Dingtalk
       end
 
       private
+        def default_params
+          {}
+        end
+
         def base_url
           'service'
         end
--
libgit2 0.21.0