Abstract: With the increase of EMU (electric multiple unit) speed, the abnormal carbody vibration of high-speed EMU occurs frequently, which seriously affects the vehicle fatigue life and riding comfort. The whole vehicle modal analysis of a type of EMU is carried out. By comparing the parameters such as different lines, different speeds, inner end wall settings and wheelset reprofiling condition with the control group, the change trend of the first-order modal frequency of carbody in servicing state is studied. Test results show that the rhombic vibration main frequency of the tested EMU decreases while the running speed elevates from 300 km/h to 350 km/h, and the frequency response amplitude increases slightly; with the increase of equivalent taper, the main frequency of carbody rhombic vibration decreases obviously, while the main frequency decrease of carbody without inner end wall setting is more serious.