Ship optimization is faced with the problem of solving a long time and optimizing the efficiency. In this paper, the basic principle of variable complexity method is introduced and the optimization framework of variable complexity is given. With KCS ship wave resistance as the goal, the variable complexity method is used to optimize the KCS bow line, Ship type, and to optimize the results of comparative analysis. It can be seen from the results that the computational results of the variable complexity method have a certain reliability, which can significantly improve the efficiency of ship optimization and have certain practical value.