This paper introduces a kind of double claw-pole structure generator for self-excited retarder.Claw pole staggered on both sides of the rotor,axial magnetic circuit constituting the N-pole and S-pole magnetic pole.Based on the JMAG software, we simulated the air gap magnetic field of no-load and load generator, and studied the influence of armature reaction on the air gap magnetic field.Through the analysis of magnetic flux leakage of the generator, and the optimization of correlation structure, we drew the relationship curve about the structure parameters of the no-load motor and magnetic flux leakage coefficient, the conclusion we obtained will provide theoretical reference for the further research and optimization of this kind of motor.Finally, the no-load characteristics and load regulation characteristics of the motor were given, and it turned out that it could meet the required excitation power for self-excited retarder.