Abstract: Taking the multi-blade centrifugal fan of the blowing system of a certain model of bathroom heater with the fan as the research object, simulation analysis of the outlet air volume and uniformity of the prototype fan was carried out by ANSYS Fluent 2020 R2. The results show that the error between the simulation and the test is within 5%, which verified the reliability of the CFD numerical simulation method to optimize the volute of the multi-blade centrifugal fan of the bathroom heater. The volute profile was parameterized, and through orthogonal experimental design, the placement angle of volute tongue α, the radius of volute tongue R, the constant of equiangular spiral A（circumferential area of the volute） and the moving distance of fan L（distance between the volute tongue and fan） were selected as factors, sixteen groups of parameter combination schemes have been developed and CFD numerical simulation has been carried out. The outlet air volume and uniformity index of each scheme were obtained, and the optimal parameter combination was determined by mean value and range analysis. The numerical results show that the turbulence intensity near the volute tongue of the optimized fan is reduced, and the internal flow is improved. The test results show that the air volume of outlet of the optimized fan increases by 7.3%, the uniformity increases by 4.5%, and the total pressure efficiency increases by 5.9%. The air volume of the outlet and uniformity of wind speed distribution of the multi-blade centrifugal fan also improves significantly. It is significant for improving the heating efficiency and human comfort of the bathroom heater with the fan.