The trainnet coupling simulated model combined CRH2 type highspeed electric motor units (EMUs) with the certain actual doubletrack autotransformer (AT)structure traction net is built by multiconductor transmission line equivalent order reduction method. With the model, the influences of various factors on resonance frequency and harmonic current amplification factor of traction net when EMUs run in fixed positions, dynamic positions, different conditions and different power are analyzed. The simulation results are verified by the measured data. In the end, Ctype filter is proposed to suppress the harmonic current, and the methods of parameters design and installation location selection for filter are proposed to make sure the electrical matching between EMUs and traction nets after filtering. The corresponding suppression effects of traction net harmonic current amplification are also simulated and validated when Ctype is installed at satisfied section post (SP).