A wireless transmission performance test system is provided, configured to test wireless transmission performance of a device under test (DUT) which is disposed in a testing chamber. The wireless transmission performance test system includes a directional antenna and a control device. The directional antenna is disposed inside the testing chamber and adjacent to the DUT to receive testing signal generated by the DUT after testing. The signal coupling direction of the directional antenna is directed to the DUT. The control device is configured to receive the testing signal transmitted from the directional antenna, process the testing signal, and generate testing result. A wireless transmission performance test method is also provided herein.