Abstract: Targeting the speed limit operation problems caused by severe body hunting, excessive stability indicators that exist in certain type of foreign low-floor articulated EMU, line tests of wheel\|rail contact relationship and suspension system vibration transmission are conducted. Adopting video monitoring method of real vehicle line operation, comprehensive analysis of the vehicle body running posture, suspension system vibration transmission, structural mode and wheelset vibration is carried out. Results show that the low\|frequency wheelset hunting motion are transmitted to the vehicle body through suspension system, thus the hunting motion of vehicle body and structure rhombic modal coupling vibration are excited, which leads to the excessive stability indicators. The on\|board video monitoring method exposes that the wheelset indeed have 1 Hz low\|frequency amplitude hunting motion, with significant air spring displacement, that is, the relationship between the wheelset hunting motion and the yawing of the vehicle body is visually captured. After analysis and testing, it is confirmed that improving the profile of the tread can improve the wheel\|rail contact relationship and control the hunting motion of the wheelset to avoid abnormal hunting of the vehicle body, so that the stability of vehicle running is ensured.