In order to control low-frequency automobile engine vibration in rolling and bouncing modes, a design method for the engine mounting system using hydraulic insulators was developed. In this method, the design optimization theory for each hydraulic insulator and the theory for determining equivalent mass at mounting points for various modes, which were developed by the authors, are applied to integral sustem optimization. Computer simulation results show that the resonance pikes can be effectively controlled by hydraulic engine mount systems using this design method.