In order to achieve the optimal performance and reliability of the ion thruster in a wide power range, the influence of acceleration grid voltage and anode flow rate on the performance of ion thruster are studied experimentally and theoretically. The results show that in a certain range the ion beam current decreases continuously with the decrease of the absolute value of the accelerating voltage, and then increases suddenly. The electron backstreaming limited voltages in large and small thrust modes are –140 and –115 V, respectively. When the anode flow rate increases, the discharge voltage and discharge loss increase monotonically, and the deceleration current decreases monotonously. Under the power of 300−4850 W, the thrust is 11−188 mN, the specific impulse is 1800−3567 s, and the efficiency ranges from 34% to 67% by adjusting the anode current, grid voltage and working fluid gas flow. The maximum efficiency of thruster reaches 67% at 3000 W. This turning point is critical for thruster design and on-orbit applications. Choosing a reasonable range of working parameters can improve the performance and life of the thruster in application.