The paper discusses the optimization technology and algorithm features in the hydraulic system simulation. It presents the realization in the package. Detailed description of the principle and development is shown, focused on parameter optimization by parameter error integration and genetic algorithm which are realized in the optimization module. The application is an example of hydraulic system of injection molding machine which showed the efficiency and capacity of the module. The comparison between curves of simulation and experiment indicated the achievements, to find optimized hydraulic parameters efficiently and quickly so as to shorten the design cycle.