Hi ldjyl.
Sorry for late response. It happened that other person asked the same question recently. Here is that post.
Like I said in that post. x86 architecture has all the drivers precompiled for most of the external WiFi adapters. You have to find which chipset is being used in your WiFi adapter and find appropriate driver for Linux. Then you need to build and test it. Since it related to tweaking with kernel, I would advise you to keep your current configuration on a separate SD card and experiment with the driver on a separate, clean operating system. After you will succeed with the kernel driver, repeat steps on your normal SD card.
Best regards,
Krzysztof Wojciechowski.