Generally, the gear parameters of planetary vehicle transmission are got by the empirical design method. Some gears are damaged early because of low strength, as well as big structure size because of high strength in use. In this paper, the equal strength and minimum volume of the gear box planetary gears were regarded as optimization objective, and the assemble conditions were thought of optimization constraint. The gear parameters were obtained after calculation. Then planetary gears were analyzed by using ROMAX and the maximum of fatigue stress and fatigue life was obtained. The simulation and experiment result shows that some weak strength gears are enhanced and the whole strength is increased. The maximum gear contact stress is reduced from 1118MPa to 932MPa. The stress of all gears is more balanced and the difference of contact stress is decreased from 368MPa to 193MPa.The difference of gears figure life is shrunk from 157702h to 91588h compared to the conventional design gear life. The overall volume is reduced by 8.38%. The result is consistent with the optimization target.