Aiming at the problems of low efficiency andlow power factor of the motor in the permanent magnet synchronous power generation system of diesel locomotive, the maximum torque per ampere (MTPA) control strategy is adopted to control the traction converter, and the MTPA control under the limitation of voltage limit ellipse is analyzed. The power angle, power factor and efficiency are compared under the unity power factor control and id=0 control strategies. The simulation and comparison analysis shows that the speed regulation range of the id=0 control is very narrow, the unity power factor control is unstable at high speeds, while the MTPA control can run stably in the full speed range. Furthermore, the power factor and efficiency of the permanent magnet synchronous generator are improved with MTPA control，and the stability of the system is improved.