Abstract: Performance experiments in high-temperature molten salt conditions were carried out to solve the stability problems arising from long-shaft molten salt pumps. Based on the fluid-solid coupling analysis, the flow field in the pump and stress-strain characteristics of impeller blades in different media and working conditions were analyzed. The modal law of the rotor shaft system was investigated, and the Latin hypercube sampling method was adopted to optimize the bearing position. The results show that with the increasing molten salt temperature, the pump efficiency and head curves shift upward. The larger Reynolds number of the medium leads to smaller hydraulic loss caused by the boundary layer. The hydraulic performance of the molten salt medium at 500℃ is better than that of clear water at room temperature. Under different media and at different temperatures, the maximum stress of the impeller blade approximately positively correlates with the specific gravity of the medium. The maximum deformation of the blade increases with the rising molten salt temperature. The natural frequency and amplitude of the rotor shaft system do not change much in different flow conditions. The optimization results based on Latin hypercube sampling indicate that the bearing support should be arranged equidistant. After optimization, the first-order critical speed of the shaft system is about 31% higher than that of the original sample, which effectively avoids the risk of resonance of the rotor shaft system during operation.