Abstract: Based on multi body dynamics theory, a straddle monorail vehicle dynamics model is established by UM. Under condition that the track parameters and vehicle running speed remain unchanged, the evaluation indexes of curve passing performance of straddle monorail vehicle are simulated and analyzed by changing the size of horizontal wheel vertical stiffness. Results show that within the change range of vertical stiffness of horizontal wheels, the vibration acceleration and ride stability indexes of the vehicle body all meet the relevant national standards, and the evaluation grades are all excellent. With the increase of horizontal wheel vertical stiffness, the vehicle curve passing performance becomes better, however, the vehicle vibration acceleration and stationary index gradually increased, making ride comfort declined. When the vertical stiffness of horizontal wheel increases to a certain extent, the vehicle′s curve passing performance is less affected.