Abstract: In order to study the impact of the rear impeller on the hydraulic performance of the counter-rotating axial flow pump, CFD software was used to carry out numerical model calculation of the coun-ter-rotating axial flow pump device. Initially, the hydraulic performances of the front impeller and the rear impeller were compared and analyzed, and the influence of the inlet angle of the rear impeller on the hydraulic characteristics of the entire device was studied. Finally, the reliability of the data was verified through model tests. The results show that under the design conditions, the head of the coun-ter-rotating axial flow pump is 11.32 m, with an efficiency of 87.57%. Under low flow conditions, when the flow rate is about 300 L/s, it enters the saddle area in advance with a head of 14.06 m and an efficiency of 79.48%. Under high flow rate conditions, when the flow rate is 440 L/s, a head of 2.24 m with an efficiency of 54.16% is recorded. The flow inlet angle of the rear impeller of the coun-ter-rotating pump is greater than that of the front impeller, which leads to the enhancement of the wor-king ability of the rear impeller blades and the increase of the head of the rear impeller. By changing the placement angle of the rear impeller, especially under small flow conditions, the saddle area of the rear impeller is also advanced, and the inlet liquid flow angle of the rear impeller is almost the same. The research results provide a reference for the design and optimization of the rear impeller of the counter-rotating axial flow pump.