The Maxwell model, which was the simplified model of anti-yaw damper, was introduced. High-speed EMUs model wasestablished by using SIMPACK. Based on nonlinear and linear stability analysis, the influence of anti-yaw damper series stiffness withdifferent primary longitudinal stiffness and equivalent conicity on critical speed was studied. It showed that the influence of anti-yawdamper series stiffness with different primary longitudinal stiffness on critical speed was different. The anti-yaw damper series stiffnesswith different primary longitudinal stiffness and equivalent conicity had different optimal value.