With the large increase of the capacity of large nuclear / thermal power stations, high power hydraulic coupling is the core component of the main boiler feed water pump, and the strength of working impeller has become an important factor affecting the safety and stability of the power station system. In this paper, the impeller assembly body of a certain hydraulic coupler was taken as the research object. A fluid solid coupling analysis model of the full flow passage was established by the one way fluid solid coupling calculation method. The contact algorithm was used in the end face location of the pump wheel and the turbine sleeve, and the beam element was used to simulate the screw connection effect, calculation and analysis of strength of impeller assembly structure under typical working conditions. The results show that the overall deformation and stress of the assembly increase with the increase of the rotational speed ratio, and the deformation size of the impeller is basically proportional to the length of the rotation radius in the corresponding region. It shows that the centrifugal load is the main reason that affects the strength of the assembly body of the impeller, and the local stress concentration in the connection area of the impeller appears due to the screw pretightening force effect. The inner edge of the turbine sleeve is the weak area of the impeller assembly structure strength, and the analysis results are consistent with the existing results. This research work provides an effective theoretical guidance for the structural design and optimization of the impeller of the autonomous high-power hydraulic coupling.