In order to study the influence of splitter blades on the performance of mixed-flow pumps with the effects of fluid-solid interaction, a certain type of mixed-flow pump with large flow was used as the research object, and the two-way fluid-solid interaction coupling method with dynamic mesh deformation was used. The influence of the presence of splitter blades on the unsteady pressure fluctuations and the resulting structural dynamic characteristics of the mixed-flow pump were studied. It was found that the presence of splitter blades greatly reduced the maximum value of pressure fluctuation amplitude which was induced by rotor stator interaction. However, the presence of splitter blades had an effect of reducing the rate of fluctuation dissipation. The splitter blades had little influence on the average value of the axial force. When the effects of fluid-solid interaction were considered, the average value of axial force was reduced and there were fluctuations. Besides, the presence of splitter blades had an effect of reducing the fluctuation amplitude of total stress and deformation. The maximum stress area occurred in the intersection of the blade and the hub/shroud. The maximum stress of the blade was reduced by the presence of splitter blades, and the stress gradient was reduced, resulting a more uniform stress distribution. The blade deformation was more uniform in the circumferential direction due to the presence of splitter blades, and the eccentricity of the deformation distribution was reduced. The research results could provide some references for the optimal design of the mixed-flow pump.