试试这个：

     [self.m_webView loadRequest:[NSMutableURLRequest requestWithURL:[NSURL fileURLWithPath:_m_filePath]cachePolicy:NSURLCacheStorageAllowedInMemoryOnly timeoutInterval:3.0]];  

您可以更改timeoutInterval和cachePolicy，有时您需要等待更多时间才能加载。

You can change timeoutInterval and cachePolicy, in sometime you have to wait more time to loading.