The tread wear would change the wheel/rail relation and seriously affect the railway vehicle dynamic behaviors. After testing the several EMUs under running ,this paper not only analyses the discipline of tread wear, but also computers the influence on wheel/rail contact geometry by a program devopled in Matlab/GUI. A MBS model of trailer of EMUs is constructed, including the model of passagers. The dynamic performance of EMUs and riding comfort are compared among the standard, worn and turned tread profile. We draw the following conclusions：Tread profile after running for a long time without turning would emerge harmful concave worn；The unsymmetrical wheel/rail contact would increame the risk of derailment and debase passengers comfort of EMUs；After turning , the dynamic performance of EMUs can be improved.