Abstract: The flow field structure of bipolar plates has a significant impact on the performance of proton exchange membrane fuel cells, and thus its design and optimization are of great significance for the commercial development of fuel cells. The variable diameter channel design can significantly improve the mass transfer capacity of the cathode side flow field of bipolar plates, thereby enhancing the performance of single cells and their drainage capacity. However, the influence of different combinations of variable diameter channel sizes and distribution forms on fuel cell performance still lacks systematic research. In this study, an electrochemical simulation method was used to systematically compare the performance differences of fuel cells under different combinations of variable diameter structure sizes and distribution forms. The results show that the high-throughput channel design can effectively improve the overall performance of fuel cells, while the gradient change channel design does not bring significant performance improvements.