Abstract: Axial flow pumps serve as the core equipment for waterjet propulsion systems and water diversion projects. Research indicates that under low-flow conditions, flow separation-induced stall phenomena induce hump-shaped characteristics in head-flow curves. The presence of such unstable flow features poses significant operational risks to pump systems. This study proposes a flow control method based on endwall injection to suppress rotating stall in an axial flow pump. Experimental studies were conducted in terms of steady-state endwall injection and pulsed endwall injection for the axial flow pump. The influence of injected flow rate, injector numbers and pulsed injection frequency on the performance of the axial flow pump was analyzed. The injected flow rate was normalized against the design flow rate of the axial flow pump. In the experiment, the tested range of injected flow rate spanned from 2.6% to 10.48%. The number of injectors varied between 1 and 6, while the pulsed injection frequency covered a range of 0.05 Hz to 0.5 Hz. The mechanism by which the endwall injection improved the stability of the axial flow pump was revealed using pressure pulsation testing. Experiments were performed on a closed-loop axial flow pump test rig at the State Key Laboratory of Water Engineering Ecology and Environment in Arid Area, Xi’an University of Technology. The test pump was designed with a flow rate of 168 m³/h, head of 3.12 m, and rotational speed of 1800 r/min. The research results indicate that the injected mass flow rate, injector number, and pulsed injection frequency have a significant impact on the performance of the axial flow pump. When the steady-state endwall injection is performed, the stall margin of axial flow pump increases with the increase of injected mass flow rate and injector numbers. The pump efficiency exhibits negligible sensitivity to the injected mass flow rate when the injected mass flow rate is below 5% of the design flow. When the injected mass flow rate exceeds 8.4%, a measurable efficiency enhancement emerges. Parametric studies reveal a non-monotonic relationship between the injector number and pump efficiency, peaking at four injectors. Considering both the efficiency under the design point and stall margin, the optimal injector number is four, achieving a 1.83% improvement in the pump efficiency and 39.4% enhancement in the stall margin using an injection flow rate of 5.6%. Experimental studies on pulsed endwall injection were conducted using six injectors. Compared to steady-state endwall injection, the pulsed endwall injection achieves greater stability enhancement with reduced injected flow. The injection frequency significantly impacts the pump performance, with the stall margin generally increasing as the injection frequency rises. However, further increases in injection frequency exert little influence on the pump stability when the injection frequency exceeds 0.25Hz. Maintaining elevated injection frequency can significantly improve the pump efficiency. However, beyond a critical injection frequency threshold of 0.17 Hz, further increases in injection frequency exert negligible influence on the pump efficiency. Comprehensive consideration of both the pump efficiency and stall margin of the axial flow pump suggests that the injection frequency should exceed 0.25 Hz. When the injection frequency is 0.5 Hz, the pulsed endwall injection demonstrates superior stability enhancement compared to steady-state endwall injection. The use of 4.2% injection flow rate in the pulsed injection mode improves the stall margin of axial flow pump by 53.9% and the efficiency under the design point by 3.52%. Mechanistic analysis revealed that head decline initiates with rotating stall onset, where stall cell propagation velocity reaches 72% of impeller rotational speed. Endwall injection effectively delays stall inception caused by the rotating stall. Endwall injection with optimized parameters can completely suppress rotating stall and eliminate associated hump-shaped characteristics in head-flow curves, thereby substantially improving operational stability. In conclusion, endwall injection demonstrates dual-benefit capability by maintaining the pump efficiency under the design point while enhancing the operational stability significantly, thereby establishing itself as a critical flow control strategy for achieving high-efficiency and high-stability operation in axial flow pumps.