The response time of the high-speed on-off solenoid valve has a great influence on the performance of the automatic hydraulic transmission. In order to reduce the response time of the highspeed onoff valve, the simulation model of the dynamic performance of valve is built by use of the software AMESim. An objective function based on ITAE criterion was built and the Genetic Algorithms （GA） was used to optimize parameters including number of windings circle, working air gap， and etc. Optimization results were analyzed. Research results show that the result from a simulation based on the model is verified by that from performance test experiments while response error is 3.3%, and the simulation model can quite accurately describe the dynamic performance of the on-off valve. After optimization, the response time of the valve is reduced by 38.16%， which meets the demands of fast response in performance. The research can provide theoretical reference for further improvement of automatic hydraulic transmission performance.