A detailed investigation conducted into the mechanism of the polygonal wear of EMU train wheels is presented through extensive dynamic experiment. This paper summarizes the typical vibration characteristics, time—frequency domain transmission relationship, and the evolution and development of polygon wear. The dynamic model of the track including the rubber gasket, the fastener and the rail is established. Considering the constraint effect of the two bogies on the rails, the modal vibration characteristics of the rail are analyzed. The frequency components directly related to the frequency of the polygonal wear of the wheel are analyzed. The frequency source of the wheel polygon problem is determined. The relationship between the relative vibration frequency, wheel rotation frequency and wheel polygon frequency is established.