Based on the theory of force transmissibility,the model of a vibration isolation system was established through an example.Applying finite element method software,optimization design for the model was carried out.This optimization searches the optimum parameter of vibration isolator so that the force transmitted to the foundation was the minimum.Results show that the vibration isolation effect is obviously improved.This kind of optimization design method provides a reference for complex vibration system,especially for the system of asymmetrical vibration.