In order to investigate the influence of guide vane parameters on the hydraulic characteristics of a mixed-flow pump, using a model pump with a specific speed of 438 as a study object under the condition that other parameters remain constant, the hydraulic characteristics of mixed-flow pumps in four schemes of different numbers of guide vane blades and in seven schemes of different sweep angles of guide vane blades were numerically simulated using the computational fluid dynamics method based on model test verification. The results show that the number of guide vane blades has a significant effect on the external characteristics of the mixed-flow pump. Different optimal numbers of guide vane blades exist for different discharges: the number of guide vane blades should be appropriately increased under low discharge conditions, and it should be appropriately reduced under large discharge conditions. The sweep angle significantly influences the hydraulic characteristics in the large discharge area. Different optimal sweep angles exist for different discharges. The optimal sweep angle changes from -16° to +24° with the increase of discharge, and the influence of the sweep angle within the computational range on the efficiency reaches 5. 5% when the discharge is 510L/s.