Abstract: Three kinds of diagonal flow fans with different blade angles for locomotives are designed by the axial flow fan design method and the S₂ calculation method, and the three-dimensional Reynolds averaged N-S equations and the SST turbulence model are used to simulate the flow field and aerodynamic performance of the diagonal flow fan. An experiment is used to test the fan performance. The results show that the blade angles of leading edge, middle region, and trailing edge have great effect on the flow field and aerodynamic performance of the diagonal flow fan. When the blade angles of the leading edge and the trailing edge increase 8°-10° with the reduction of the difference between the blade angles of the middle region and the trailing edge, the efficiency curve of the diagonal flow fan presents a parabolic distribution, and the efficiency can be improved by 5%. In the same conditions, the pressure distribution of the suction surface of the blade front tends to be smooth; the pressure distribution of the pressure surface at the location of 5% span is largely improved; the separation zone and separation flow loss reduce significantly; and the blade load distribution is increasingly uniform. The performance of diagonal flow fan is compared between that from the simulation and from the experiment. The difference of total pressure is only 3%, and the efficiency difference is less than 4%. The result are consistent.