Abstract: Using the gearbox system analysis software MASTA and the large-scale general CAE software MSC Patran & Nastran, the meshing analysis model and the box finite element model of the marine gearbox are established.The load of the gearbox under multiple loading cases is analyzed and compared, and the structural efficiency are analyzed and evaluated.Based on the principle of stress field balance and the constraint of strength and stiffness, the lightweight structure of the box is designed to reduce redundant materials.Through the modal analysis of the lightweight box, the resonance of the gearbox system is avoided.At present, the high power marine gearbox with this method has been mass-produced, and the weight of the gearbox box has been reduced by 19% after lightweight, so as to achieve the purpose of lightweight.