diff --git a/config/config.php b/config/config.php
index b89b4eecd1..97e70cc343 100644
--- a/config/config.php
+++ b/config/config.php
@@ -47,12 +47,19 @@ $config->default->method = 'index';       // Default method.
 $config->file->dangers = 'php,jsp,py,rb,asp,'; // Dangerous files.
 $config->file->maxSize = 1024 * 1024;          // Max size.
 
-/* Database settings. */
-$config->db->persistant = false;           // Pconnect or not.
-$config->db->driver     = 'mysql';         // Must be MySQL. Don't support other database server yet.
-$config->db->encoding   = 'UTF8';          // Encoding of database.
-$config->db->strictMode = false;           // Turn off the strict mode of MySQL.
-$config->db->checkCentOS= true;            // Whether check is centos or not, thus to fix the error of pdo in centos.
+/* Master database settings. */
+$config->db->persistant = false;     // Pconnect or not.
+$config->db->driver     = 'mysql';   // Must be MySQL. Don't support other database server yet.
+$config->db->encoding   = 'UTF8';    // Encoding of database.
+$config->db->strictMode = false;     // Turn off the strict mode of MySQL.
+$config->db->checkCentOS= true;      // Whether check is centos or not, thus to fix the error of pdo in centos.
+
+/* Slave database settings. */
+$config->slaveDB->persistant = false;      
+$config->slaveDB->driver     = 'mysql';    
+$config->slaveDB->encoding   = 'UTF8';     
+$config->slaveDB->strictMode = false;      
+$config->slaveDB->checkCentOS= true;       
 
 /* Include the custom config file. */
 $myConfig = dirname(__FILE__) . DIRECTORY_SEPARATOR . 'my.php';
diff --git a/framework/router.class.php b/framework/router.class.php
index 992487ebd0..f4bf431e66 100755
--- a/framework/router.class.php
+++ b/framework/router.class.php
@@ -131,7 +131,7 @@ class router
     /**
      * The control object of current module.
      * 
-     * @var string
+     * @var object
      * @access public
      */
     public $control;
@@ -195,7 +195,7 @@ class router
     /**
      * The global $config object.
      * 
-     * @var string
+     * @var object
      * @access public
      */
     public $config;
@@ -203,7 +203,7 @@ class router
     /**
      * The global $lang object.
      * 
-     * @var string
+     * @var object
      * @access public
      */
     public $lang;
@@ -211,11 +211,19 @@ class router
     /**
      * The global $dbh object, the database connection handler.
      * 
-     * @var string
+     * @var object
      * @access private
      */
     public $dbh;
 
+    /**
+     * The slave database handler.
+     * 
+     * @var object
+     * @access private
+     */
+    public $slaveDBH;
+
     /**
      * The $post object, used to access the $_POST var.
      * 
@@ -1459,26 +1467,39 @@ class router
      */
     public function connectDB()
     {
-        global $config, $dbh;
-        if(!isset($config->db->driver)) self::error('no pdo driver defined, it should be mysql or sqlite', __FILE__, __LINE__, $exit = true);
-        if(!isset($config->db->user)) return false;
-        if($config->db->driver == 'mysql')
+        global $config, $dbh, $slaveDBH;
+
+        if(isset($config->db->host))      $this->dbh      = $dbh      = $this->connectByPDO($config->db);
+        if(isset($config->slaveDB->host)) $this->slaveDBH = $slaveDBH = $this->connectByPDO($config->slaveDB);
+    }
+
+    /**
+     * Connect database by PDO.
+     * 
+     * @param  object    $params    the database params.
+     * @access private
+     * @return object|bool
+     */
+    private function connectByPDO($params)
+    {
+        if(!isset($params->driver)) self::error('no pdo driver defined, it should be mysql or sqlite', __FILE__, __LINE__, $exit = true);
+        if(!isset($params->user)) return false;
+        if($params->driver == 'mysql')
         {
-            $dsn = "mysql:host={$config->db->host}; port={$config->db->port}; dbname={$config->db->name}";
+            $dsn = "mysql:host={$params->host}; port={$params->port}; dbname={$params->name}";
         }    
         try 
         {
-            $dbh = new PDO($dsn, $config->db->user, $config->db->password, array(PDO::ATTR_PERSISTENT => $config->db->persistant));
+            $dbh = new PDO($dsn, $params->user, $params->password, array(PDO::ATTR_PERSISTENT => $params->persistant));
             $dbh->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_OBJ);
             $dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
-            $dbh->exec("SET NAMES {$config->db->encoding}");
-            if(isset($config->db->strictMode) and $config->db->strictMode == false) $dbh->exec("SET @@sql_mode= ''");
-            if(isset($config->db->checkCentOS) and $config->db->checkCentOS and helper::isCentOS())
+            $dbh->exec("SET NAMES {$params->encoding}");
+            if(isset($params->strictMode) and $params->strictMode == false) $dbh->exec("SET @@sql_mode= ''");
+            if(isset($params->checkCentOS) and $params->checkCentOS and helper::isCentOS())
             {
                 $dbh->setAttribute(PDO::ATTR_EMULATE_PREPARES, true);
                 $dbh->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, true);
             }
-            $this->dbh = $dbh;
             return $dbh;
         }
         catch (PDOException $exception)
diff --git a/lib/dao/dao.class.php b/lib/dao/dao.class.php
index 4c35154e6e..d8fc06ee8d 100755
--- a/lib/dao/dao.class.php
+++ b/lib/dao/dao.class.php
@@ -56,6 +56,14 @@ class dao
      */
     protected $dbh;
 
+    /**
+     * The global slaveDBH(database handler) object.
+     * 
+     * @var object
+     * @access protected
+     */
+    protected $slaveDBH;
+
     /**
      * The sql object, used to creat the query sql.
      * 
@@ -130,11 +138,12 @@ class dao
      */
     public function __construct()
     {
-        global $app, $config, $lang, $dbh;
-        $this->app    = $app;
-        $this->config = $config;
-        $this->lang   = $lang;
-        $this->dbh    = $dbh;
+        global $app, $config, $lang, $dbh, $slaveDBH;
+        $this->app      = $app;
+        $this->config   = $config;
+        $this->lang     = $lang;
+        $this->dbh      = $dbh;
+        $this->slaveDBH = $slaveDBH ? $slaveDBH : false;
 
         $this->reset();
     }
@@ -476,8 +485,17 @@ class dao
         $sql = $this->processSQL($autoCompany);
         try
         {
+            $method = $this->method;
             $this->reset();
-            return $this->dbh->query($sql);
+
+            if($this->slaveDBH and $method == 'select')
+            {
+                return $this->slaveDBH->query($sql);
+            }
+            else
+            {
+                return $this->dbh->query($sql);
+            }
         }
         catch (PDOException $e) 
         {