What do you mean by "my host could not recognize galileo usb"?
If you only use the SPI image on the Galileo, isn't it appearing on your PC's device manager? But if you use the the Yocto full image it does appear?
Did you make sure, to update the Galileo's firmware with the Intel® Galileo Firmware Updater?
Could you add a few screenshots explaining your issue?
thanks for your reply
i realized that my sd card image which compiled by myself may not include drivers of usb client port.
because it works well when i use your official sd card image instead of mine.
I see, I'm glad to hear that you found out the root of your issue.