In order to improve the reliability of light high- speed marine gearbox design,the finite element method is adopted to establish the finite element statics model of the gearbox body. Through the analysis of the simulation software,the displacement and stress distribution of the box body ahead running and reverse condition are computed. According to the analysis results in the weak structure,the box structure is optimized. The strength of the optimized gearbox tends to be uniform and the structure is more reasonable than previous design,a foundation for the manufacture of the gearbox is provided.