In order to design high-performance, low-cost magnetic gears(MG), this paper presents an optimized design method which comprehensively considers the torque density and the permanent magnet(PM) utilization. The objective function of optimization analysis is defined. The design method of key parameters under the MG with different gear ratio is systematically analyzed by finite element analysis (FEA). And the coupling optimization law between various parameters is revealed. Finally, the prototype was made according to the optimization results, which torque density reached 111.3N.m/L and PM utilization reached 67.4N.m/kg. The research has significant value in the engineering domain.