Universal serial bus device test system and its method

The present invention relates to a universal serial bus speed testing system and method applied to a computer means with a universal serial bus test fixture. First, the memory buffer size allocated computer device side to adjust the transmission unit of the computer device a universal serial bus speed test data. And when the speed of the test data from the memory buffer is full test fixture universal serial bus test data input buffer, sending an interrupt signal to the microprocessor control unit universal serial bus test fixture. Next, the control unit discards the microprocessor speed test data, and return a response to the test data output buffer flag universal serial bus test fixture. Finally, the test program transmits a response to the flag in the computer apparatus, to confirm the complete speed test. The present invention can improve the stability of the test and the test speed Universal Serial Bus.