Excessive underground train-induced building vibration is an environmental concern resulting in human distress. Wheel polygon is probably one of the main vibration sources. In the present work, an explicit-integration time-domain, fully coupled 3D dynamic train-track-tunnel-soil-building FE model is developed and employed to investigate the effects of wheel polygon on the building vibration. Measured wheel polygon data is analyzed and input into the developed FE model. Based on the simulation results, it is found that the contribution of the wheel polygon to the building vibration is considerable in the frequency range from 30 to 180 Hz. Wheel polygon makes the building vibration more pronounced at the P2 resonance frequency and the passing frequencies (f = v/λ) of wheel polygon. From the foundation to a high floor in the building, the effect of the P2 resonance-related wheel polygon attenuates the slowest while the effects of the other orders of wheel polygon attenuate fast.