In order to investigate the flow field characteristics of low-specific-speed centrifugal pump under multi-conditions, ten different design cases were simulated and their performances were predicted, and the impact of key geometric parameters of impeller and volute on performance and flow field were discussed. The comparative experiments on location of splitter blades and volute throat area were carried out. The investigation results showed that the head increased by 5.5 m and the efficiency increased by 3.23% in the optimal case D by adding splitter blades. Through increasing the area of volute flow and throat, the head in all of the five cases improved by 10 m approximately, efficiency improved by about 5%, which could expand the high-efficiency scope and improve maximum efficiency. The investigation can provide certain scientific basis for the performance optimization of low-specific-speed centrifugal pump.