The centrifugal pump is the key equipment for power conversion in the CAP1400 power plant. According to the equipment layout requirements in the nuclear power plant process system design manual, the pipe section at the entrance should be a straight pipe with a length at least five times the pipe diameter. However, in actual layout, due to factors such as plant space or modularity, the layout of the inlet pipes of some centrifugal pumps cannot meet this requirement, resulting in non-uniform incoming flow at the pump inlet, which affects the safe and stable operation of the pump and system. In this paper, two different structures of rectifiers are designed and numerically simulated for the elbow part of the inlet pipe section of the SFS system centrifugal pump in the CAP1400 power plant. Firstly, the variation of flow uniformity of the pump inlet pipe at different inlet speeds is studied. Then, the influence of different structure rectifiers on the uniformity of flow at the pump inlet under the same working conditions is studied. The results show that the addition of a rectifier in the elbow can effectively improve the flow uniformity of the pump inlet section and reduce the effect of uneven inlet flow on the pump performance.