Abstract: The volute of a 30 kW air compressor for a hydrogen fuel cell system was taken as the object of optimization. Aerodynamic performance tests were conducted on the original prototype， and CFD simulation of the whole machine was performed， revealing good consistency between the experimental and simulated results. Based on the prototype’s impeller and vaneless diffuser， the volute was redesigned for better matching. Numerical simulations were carried out on centrifugal compressors with the same impeller and diffuser but different volute parameters， leading to the development of a new cross-section-shaped volute suitable for hydrogen fuel cell air compressors. By analyzing the influences of different volute parameters on overall compressor performance and internal air flow， the optimal combination of parameters was determined. After the optimization， the total pressure ratio increases by 8.20%， efficiency improves by 1.91%， and the air flow in the new volute becomes more uniform.