Taken the opening of the hull girder web as the research object, considering the complex loading conditions of the hull, based on the compromise planning method with the satisfaction weight factor, the traditional Bidirectional Evolutionary Structural Optimization (BESO) method is improved. Taken volume reduction ratio as the optimization target, with the side stress as a constraint, a method for optimizing the hole shape of the hull structures is proposed. On this basis, based on ANSYS software, through secondary development, an improved BESO optimization program is written to optimize the design of the waist circle opening of the hull girder web, and an opening pattern with uniform stress distribution and obvious weight loss is obtained. The optimization results show that under the condition of satisfying the structural strength, the weight of the hull girder web is reduced by 30.01%, achieving the purpose of light weight. The research results can provide reference for the optimization of ship structure design.