您可以使用：

public void onBackPressed()  
{  
    //do whatever you want the 'Back' button to do  
    //as an example the 'Back' button is set to start a new Activity named 'NewActivity'  
    this.startActivity(new Intent(YourActivity.this,NewActivity.class));  

    return;  
}  

在这里看看：http://www.41post.com/1685/programming/android-changing-the-back-button-behaviour