How to make fastboot work?

[ldqmoon]

dear all
i'm using A20-OLinuXino-MICRO-4GB and I try to use fastboot to flash my new u-boot.
but I found some problem,
this is my step

- enter u-boot by press space during boot
- type fastboot in the command line and the board enter fastboot mode
- win8.1 find a driver and install it.
- in win8.1,command line, I type fastboot devices, but no device shows

I found the device driver in win8.1 is ADB interface, while it should be bootloader interface after google the reason.
I tried some driver from google but still can not find bootloader driver.

anything wrong with my step? or how to make fastboot work?
kindly thanks