Abstract: The magnetic field strength directly influences the probability of the primary electrons making a collision before being lost to the anode. Based on the analytical discharge performance model and the experimental values of the beam ion energy cost,The artide considers that only by changing the magnetic field strength to improve the performance of the ion thruster,while keeping the LIPS-200 configuration and operation parameters unchanged. The results show that reducing the size of the magnet for 1 mm,the magnetic density flux contour in the discharge chamber would be changed and the strength of the magnet transforms from the 5.0×10^-33.0×10^-2T to 1.0×10^-25.0×10^-2T. By increasing the strength50%,the mean time for a primary electron wouldbe decreased by 49.9%,the probability of collision between the primary electrons and neutrals would be increased by 6.9%,the loss rate of the ion would be reduce by 64%,the beam ion energy cost would be decreased by 18.1%,and the propellant utilization would be improved by 7.4%.The results can provide reference and reference value in the future development of the performance analysis of ion thruster.