The use of damping system can significantly reduce the shock and vibration experienced by inertial measurement unit (IMU), and improve the measurement accuracy and the final navigation result. Firstly, modal analysis of IMU damping system was studied using finite element software Patran/Marc and the damping system main modal frequencies and shapes were obtained. Secondly, the influence on the modal analysis imposed by three key factors, such as temperature, axes-compression and radial-compression of damping rubber module, were analyzed with the simulation method. Then an optimized design of an IMU damping system was presented. The results show that the parameters in the damping system can be adjusted by changing the structure parameters, and the application demand of dither laser gyro INS are satisfied.