Abstract: The discharge chamber parameters of annular ion thruster have a significant influence on its thrust and spe-cific impulse.The steady-state discharge process of annular ion thruster is simulated by the decoupling iterative algorithm based on the hybrid Particle-in-cell:(Hybrid-PIC)method.It is found that the parameters of discharge chamber will affect the thrust,specific impulse,discharge loss,ionization rate and the uniformity of ion distribution at the outlet of discharge chamber.The results show that for the annular ion thruster,increasing the cathode length reduces the loss of primary elec-trons and plasma on the anode wall,and improves their uniformities.Increasing the number of magnets has little effect on the free motion range of primary electron,so it has little effect on the plasma distribution.Increasing the channel width to diameter ratio can increase the free motion range of primary electron,hence improving the uniformities of the primary electrons and plasma.Reducing the inner diameter makes the improvement more significant.Therefore,the cathode length of the 5 kW annular ion thruster should be 1.5 times of the design length,and the channel width to diameter ratio should be 1.2 times of the design value.