Abstract: Pressurizer is an important componentin nuclear power plant, whose weight and dimension influence the weight, volume and arrangement of nuclear power plant. The designoptimization ofnet volume of pressurizer was carried out based on a complex-genetic algorithm, which is a self-developed method. The results show that optimal volume is 40.9% less than original, and the optimization effect is obvious. The effects of operation parameters of primary loop on the net volume of pressurizer were also analyzed in order toprovide reference for engineering design.