The　structure　design　and　material　selection　optimization　of　the　secondary　transmission　planetary　reducer　gear　are　carried　out,　and　the　lightweight　design　is　carried　out　under　the　condition　of　meeting　the　contact　fatigue　strength　and　bending　fatigue　strength;　the　optimized　gear　is　simulated　by　using　the　transient　dynamics　module　of　finite　element,　which　provides　a　new　method　to　reduce　the　mass　of　planetary　reducer　and　improve　its　overall　power　density　reference　resources.　©　2020　ACM.