By constructing a dynamic model of subway vehicles that includes air springs, the dynamic data of the air springs were selected. The main optimized parameters are the lateral stiffness and vertical stiffness of the air spring, and the main evaluation indicators include the vehicle’s motion stability, running smoothness, and running safety (curve passing performance). The research results indicate that an increase in vertical stiffness will lower the critical speed of the vehicle. An increase in the horizontal stiffness of the air spring will have a slight impact on the lateral stability index, while an increase in vertical stiffness will significantly affect the vertical stability index, but will reduce the lateral vibration of the frame. Considering all factors, it is recommended that the lateral stiffness of the secondary air spring be 0.15 MN/m and the vertical stiffness be 0.35 MN/m.