Taking the bearing capacity increasing,meeting the equal strength design and the minimum center distance of gear drive as objective function,the multi- objective optimum design mathematical model of the two- grade helical cylindrical gear drive is established. The optimization solution is carried out by using NSGA- II algorithm,the multi- objective optimization design of two- grade helical cylindrical gear drive is carried out,and the Pareto optimal solutions are obtained. The result shows that the strength and the stable reliability of the optimal scheme is enhanced in terms of ensuring the equal contacting strength and the center distance has certain decrease.