With the development of railway transit wireless communication technology, the existing test platforms about comprehensive test are facing new challenge of real-time problems. Aiming at the demand for Doppler Effect testing of domestic railway transit WLAN equipment and in consideration of the flaw of small bandwidth and relatively large delay of the channel emulator, this paper proposes a novel approach for the real-time simulation of Doppler Effect channel. We build a test platform by the use of dual-Doppler channel emulators, and then combine it with path loss circuit to implement the comprehensive performance test of WLAN system in high-speed environment. This platform provides an integrated solution for system access test of railway transit's WLAN system.