diff --git a/autojs/src/main/assets/modules/__io__.js b/autojs/src/main/assets/modules/__io__.js
index ad382866..5e826c3d 100644
--- a/autojs/src/main/assets/modules/__io__.js
+++ b/autojs/src/main/assets/modules/__io__.js
@@ -1,8 +1,10 @@
 
 module.exports = function(__runtime__, scope){
-    var files = Object.create(com.stardust.autojs.runtime.api);
-    files.cwd = function(){
-        return scope.engines.myEngine().cwd();
+    var fs = __runtime__.files;
+    var files = Object.create(fs);
+    files.join = function(base){
+        var paths = Array.prototype.slice.call(arguments, 0);
+        return fs.join(base, paths);
     }
     scope.files = files;
     scope.open = function(path, mode, encoding, bufferSize){
diff --git a/autojs/src/main/java/com/stardust/autojs/runtime/ScriptRuntime.java b/autojs/src/main/java/com/stardust/autojs/runtime/ScriptRuntime.java
index ce0a6f03..c7617ae9 100644
--- a/autojs/src/main/java/com/stardust/autojs/runtime/ScriptRuntime.java
+++ b/autojs/src/main/java/com/stardust/autojs/runtime/ScriptRuntime.java
@@ -18,6 +18,7 @@ import com.stardust.autojs.runtime.api.Console;
 import com.stardust.autojs.runtime.api.Device;
 import com.stardust.autojs.runtime.api.Engines;
 import com.stardust.autojs.runtime.api.Events;
+import com.stardust.autojs.runtime.api.Files;
 import com.stardust.autojs.runtime.api.Floaty;
 import com.stardust.autojs.core.looper.Loopers;
 import com.stardust.autojs.runtime.api.Threads;
@@ -169,6 +170,9 @@ public class ScriptRuntime {
     @ScriptVariable
     public final Colors colors = new Colors();
 
+    @ScriptVariable
+    public final Files files;
+
     private Images images;
 
     private static WeakReference<Context> applicationContext;
@@ -197,6 +201,7 @@ public class ScriptRuntime {
         dialogs = new Dialogs(app, uiHandler, bridges);
         device = new Device(uiHandler.getContext());
         floaty = new Floaty(uiHandler, ui, this);
+        files = new Files(this);
     }
 
     public void init() {
diff --git a/autojs/src/main/java/com/stardust/autojs/runtime/api/Files.java b/autojs/src/main/java/com/stardust/autojs/runtime/api/Files.java
index 3e9d6f9b..74490f70 100644
--- a/autojs/src/main/java/com/stardust/autojs/runtime/api/Files.java
+++ b/autojs/src/main/java/com/stardust/autojs/runtime/api/Files.java
@@ -3,6 +3,9 @@ package com.stardust.autojs.runtime.api;
 import android.content.Context;
 import android.content.res.AssetManager;
 
+import com.stardust.autojs.engine.ScriptEngine;
+import com.stardust.autojs.runtime.ScriptRuntime;
+import com.stardust.autojs.script.JavaScriptSource;
 import com.stardust.pio.PFileInterface;
 import com.stardust.pio.PFiles;
 import com.stardust.util.Func1;
@@ -18,6 +21,16 @@ import java.io.OutputStream;
 
 public class Files {
 
+    private final ScriptRuntime mRuntime;
+
+    public Files(ScriptRuntime runtime) {
+        mRuntime = runtime;
+    }
+
+    public String cwd() {
+        return ((ScriptEngine.AbstractScriptEngine) mRuntime.engines.myEngine()).cwd();
+    }
+
     public static PFileInterface open(String path, String mode, String encoding, int bufferSize) {
         return PFiles.open(path, mode, encoding, bufferSize);
     }
@@ -218,7 +231,7 @@ public class Files {
         return PFiles.isEmptyDir(path);
     }
 
-    public static String join(String parent, String child) {
+    public static String join(String parent, String... child) {
         return PFiles.join(parent, child);
     }
 
diff --git a/common/src/main/java/com/stardust/pio/PFiles.java b/common/src/main/java/com/stardust/pio/PFiles.java
index d0a92abe..fb899ef9 100644
--- a/common/src/main/java/com/stardust/pio/PFiles.java
+++ b/common/src/main/java/com/stardust/pio/PFiles.java
@@ -409,8 +409,12 @@ public class PFiles {
         return file.isDirectory() && file.list().length == 0;
     }
 
-    public static String join(String parent, String child) {
-        return new File(parent, child).getPath();
+    public static String join(String base, String... paths) {
+        File file = new File(base);
+        for (String path : paths) {
+            file = new File(file, path);
+        }
+        return file.getPath();
     }
 
     public static String getHumanReadableSize(long bytes) {