Torque ripple is an important factor affecting the torque characteristics of IPM oil submersible motor. The purpose of reducing torque ripple is achieved through the design of the magnetic flux barrier of the motor rotor. Taking the 10 pole 12 slot IPM "一" magnet type oil submersible motor as the basic model. The two-dimensional transient field of oil submersible motor rotor is analyzed by finite element method. Based on the influence of flux barrier effect on the radial flux density of air gap, the distribution of radial electromagnetic characteristics of oil submersible motor rotor under various operating conditions is obtained, and the torque characteristics such as cogging torque and electromagnetic torque are compared and studied respectively. After optimization, the torque ripple of oil submersible motor is significantly reduced. Finally, the results verify that the design of magnetic flux barrier has a good inhibitory effect on the cogging torque of oil submersible motor. Because the stator structure of submersible motor is limited, the optimal design of flux barrier is great significance.