In order to explore the stability of the impeller structure of the mixed-flow water jet propulsion pump during operation, based on the method of unidirectional fluid-solid coupling, static and modal analyses of the impeller structure under variable flow and variable speed conditions were carried out. The results show that the maximum equivalent stress on the back of the impeller and the working surface of the water jet propulsion pump occurs at the root of the blade; the maximum displacement of the back of the impeller and the working surface occurs near the edge of the impeller outlet; the influence of flow rate change on the natural frequency of the impeller structure can be approximately ignored, and the decrease value is 0.02~0.07 Hz; compared to the influence of flow rate on the impeller structure, the change of speed has a greater impact on the impeller structure, and its increase is 0.14~1.91 Hz; the impeller speed shall not exceed 4 000 r/min, otherwise it is very easy to induce impeller resonance.