Based on the simulation model of pressure-regulating valve of tractor-brake, a hydraulic torque converter was developed. With Niche genetic algorithms, the optimal result of pressure-regulating valve was obtained. In the process of optimization, the simulation model used Matlab and ITAE was calculated as optimal target value. Finally, dynamic performance was tested in a performance experiment. The results indicated that based on simulation model, the performance of pressure-regulating valve was improved with Niche genetic algorithms and the design process was simplified. 