In order to harmonize the conflict between running stability and curve negotiation performance of highspeed railway vehicle, a multiobjective optimization method is adopt to optimize the key parameters of suspension system. A 62degree freedom highspeed railway vehicle model is built by using multibody dynamics technology. Various nonlinear factors are considered including nonlinear wheel/rail contact (geometry), nonlinear wheel/rail creep force vs. creepage, nonlinear damping forces, etc. The traditional suspension system model of vehicle is parameterized by using ADAMSMatlab cosimulation method. The stiffness and damping coefficient of the model can be adjusted. The parameters of suspension system are optimized by using multiobjective GA toolbox. The optimization results show that the running stability and curve negotiation performance can be improved greatly. Although the ride comfort performance is decreased slightly, the values can be accepted.