diff --git a/base.php b/base.php
index 32e55f3c..a73fe8b7 100644
--- a/base.php
+++ b/base.php
@@ -18,6 +18,7 @@ define('THINK_VERSION', '5.0.0beta');
 defined('DS') or define('DS', DIRECTORY_SEPARATOR);
 defined('THINK_PATH') or define('THINK_PATH', dirname(__FILE__) . DS);
 defined('LIB_PATH') or define('LIB_PATH', THINK_PATH . 'library' . DS);
+defined('EXTEND_PATH') or define('EXTEND_PATH', THINK_PATH . 'extend' . DS);
 defined('MODE_PATH') or define('MODE_PATH', THINK_PATH . 'mode' . DS); // 系统应用模式目录
 defined('CORE_PATH') or define('CORE_PATH', LIB_PATH . 'think' . DS);
 defined('ORG_PATH') or define('ORG_PATH', LIB_PATH . 'org' . DS);
diff --git a/library/think/loader.php b/library/think/loader.php
index 30fb74ed..c0c2748b 100644
--- a/library/think/loader.php
+++ b/library/think/loader.php
@@ -34,24 +34,20 @@ class Loader
         } elseif ($file = self::findFileInComposer($class)) {
             include $file;
         } else {
-            // 项目命名空间
-            $path = APP_PATH;
             // 命名空间自动加载
             $name = strtolower(strstr($class, '\\', true));
             if (isset(self::$namespace[$name])) {
                 // 注册的命名空间
                 $path = dirname(self::$namespace[$name]) . DS;
-            } elseif (in_array($name, ['think', 'org', 'behavior', 'com', 'traits']) || is_dir(LIB_PATH . $name)) {
+            } elseif (in_array($name, ['think', 'behavior', 'traits']) || is_dir(LIB_PATH . $name)) {
                 // Library目录下面的命名空间自动定位
                 $path = LIB_PATH;
+            } elseif (is_dir(EXTEND_PATH . $name)) {
+                // 扩展类库命名空间
+                $path = EXTEND_PATH;
             } else {
-                $extend = Config::get('extend_library') ?: [];
-                foreach ($extend as $_extend) {
-                    if (is_dir($_extend . $name)) {
-                        $path = $_extend;
-                        break;
-                    }
-                }
+                // 项目命名空间
+                $path = APP_PATH;
             }
             $filename = $path . str_replace('\\', DS, str_replace('\\_', '\\', strtolower(trim(preg_replace("/[A-Z]/", "_\\0", $class), "_")))) . EXT;
             if (is_file($filename)) {