diff --git a/src/emqttd.erl b/src/emqttd.erl
index 252d77d78..e57b56e0d 100644
--- a/src/emqttd.erl
+++ b/src/emqttd.erl
@@ -53,7 +53,7 @@
 -define(APP, ?MODULE).
 
 %%--------------------------------------------------------------------
-%% Bootstrap, environment, configuration, is_running...
+%% Bootstrap, environment, is_running...
 %%--------------------------------------------------------------------
 
 %% @doc Start emqttd application.
diff --git a/src/emqttd_conf.erl b/src/emqttd_conf.erl
index c4a78fd9b..5836f93a4 100644
--- a/src/emqttd_conf.erl
+++ b/src/emqttd_conf.erl
@@ -16,84 +16,91 @@
 
 -module(emqttd_conf).
 
--export([mqtt/0, retained/0, session/0, queue/0, bridge/0, pubsub/0]).
+-import(gen_conf, [value/3]).
+
+-export([mqtt/0, session/0, queue/0, bridge/0, pubsub/0]).
+
+-export([list/1]).
+
+-define(APP, emqttd).
 
 mqtt() ->
-    [
-    %% Max ClientId Length Allowed.
-    {max_clientid_len,    emqttd:conf(mqtt_max_clientid_len, 512)},
-    %% Max Packet Size Allowed, 64K by default.
-    {max_packet_size,     emqttd:conf(mqtt_max_packet_size, 65536)},
-    %% Client Idle Timeout.
-    {client_idle_timeout, emqttd:conf(mqtt_client_idle_timeout, 30)}
-    ].
-
-retained() ->
-    [
-    %% Expired after seconds, never expired if 0
-    {expired_after, emqttd:conf(retained_expired_after, 0)},
-    %% Max number of retained messages
-    {max_message_num, emqttd:conf(retained_max_message_num, 100000)},
-    %% Max Payload Size of retained message
-    {max_playload_size, emqttd:conf(retained_max_playload_size, 65536)}
-    ].
+    with_env(mqtt_protocol, [
+        %% Max ClientId Length Allowed.
+        {max_clientid_len,    value(?APP, mqtt_max_clientid_len, 512)},
+        %% Max Packet Size Allowed, 64K by default.
+        {max_packet_size,     value(?APP, mqtt_max_packet_size, 65536)},
+        %% Client Idle Timeout.
+        {client_idle_timeout, value(?APP, mqtt_client_idle_timeout, 30)}
+    ]).
 
 session() ->
-    [
-    %% Max number of QoS 1 and 2 messages that can be “inflight” at one time.
-    %% 0 means no limit
-    {max_inflight, emqttd:conf(session_max_inflight, 100)},
+    with_env(mqtt_session, [
+        %% Max number of QoS 1 and 2 messages that can be “inflight” at one time.
+        %% 0 means no limit
+        {max_inflight,         value(?APP, session_max_inflight, 100)},
 
-    %% Retry interval for redelivering QoS1/2 messages.
-    {unack_retry_interval, emqttd:conf(session_unack_retry_interval, 60)},
+        %% Retry interval for redelivering QoS1/2 messages.
+        {unack_retry_interval, value(?APP, session_unack_retry_interval, 60)},
 
-    %% Awaiting PUBREL Timeout
-    {await_rel_timeout, emqttd:conf(session_await_rel_timeout, 20)},
+        %% Awaiting PUBREL Timeout
+        {await_rel_timeout,    value(?APP, session_await_rel_timeout, 20)},
 
-    %% Max Packets that Awaiting PUBREL, 0 means no limit
-    {max_awaiting_rel, emqttd:conf(session_max_awaiting_rel, 0)},
+        %% Max Packets that Awaiting PUBREL, 0 means no limit
+        {max_awaiting_rel,     value(?APP, session_max_awaiting_rel, 0)},
 
-    %% Statistics Collection Interval(seconds)
-    {collect_interval, emqttd:conf(session_collect_interval, 0)},
+        %% Statistics Collection Interval(seconds)
+        {collect_interval,     value(?APP, session_collect_interval, 0)},
 
-    %% Expired after 2 day (unit: minute)
-    {expired_after, emqttd:conf(session_expired_after, 2880)}
-    ].
+        %% Expired after 2 day (unit: minute)
+        {expired_after,        value(?APP, session_expired_after, 2880)}
+    ]).
 
 queue() ->
-    [
-    %% Type: simple | priority
-    {type, emqttd:conf(queue_type, simple)},
+    with_env(mqtt_queue, [
+        %% Type: simple | priority
+        {type, value(?APP, queue_type, simple)},
 
-    %% Topic Priority: 0~255, Default is 0
-    {priority, emqttd:conf(queue_priority, [])},
+        %% Topic Priority: 0~255, Default is 0
+        {priority, value(?APP, queue_priority, [])},
 
-    %% Max queue length. Enqueued messages when persistent client disconnected,
-    %% or inflight window is full.
-    {max_length, emqttd:conf(queue_max_length, infinity)},
+        %% Max queue length. Enqueued messages when persistent client disconnected,
+        %% or inflight window is full.
+        {max_length, value(?APP, queue_max_length, infinity)},
 
-    %% Low-water mark of queued messages
-    {low_watermark, emqttd:conf(queue_low_watermark, 0.2)},
+        %% Low-water mark of queued messages
+        {low_watermark, value(?APP, queue_low_watermark, 0.2)},
 
-    %% High-water mark of queued messages
-    {high_watermark, emqttd:conf(queue_high_watermark, 0.6)},
+        %% High-water mark of queued messages
+        {high_watermark, value(?APP, queue_high_watermark, 0.6)},
 
-    %% Queue Qos0 messages?
-    {queue_qos0, emqttd:conf(queue_qos0, true)}
-    ].
+        %% Queue Qos0 messages?
+        {queue_qos0, value(?APP, queue_qos0, true)}
+    ]).
 
 bridge() ->
-    [
-    %% TODO: Bridge Queue Size
-    {max_queue_len,      emqttd:conf(bridge_max_queue_len, 10000)},
+    with_env(mqtt_bridge, [
+        %% TODO: Bridge Queue Size
+        {max_queue_len,      value(?APP, bridge_max_queue_len, 10000)},
 
-    %% Ping Interval of bridge node
-    {ping_down_interval, emqttd:conf(bridge_ping_down_interval, 1)}
-    ].
+        %% Ping Interval of bridge node
+        {ping_down_interval, value(?APP, bridge_ping_down_interval, 1)}
+    ]).
 
 pubsub() ->
-    [
-    %% PubSub and Router. Default should be scheduler numbers.
-    {pool_size, emqttd:conf(pubsub_pool_size, 8)}
-    ].
+    with_env(mqtt_pubsub, [
+        %% PubSub and Router. Default should be scheduler numbers.
+        {pool_size, value(?APP, pubsub_pool_size, 8)}
+    ]).
+
+with_env(Key, Conf) ->
+    case application:get_env(?APP, Key) of
+        undefined ->
+            application:set_env(?APP, Key, Conf), Conf;
+        {ok, Val} ->
+            Val
+    end.
+
+list(Key) ->
+    gen_conf:list(?APP, Key).