The permanent magnet synchronous power generation system of diesel locomotive needs to stably control the intermediate DC link voltage, as well as reduce the voltage pulsation within the full speed range of the internal combustion engine and under sudden load conditions. To meet these requirements, the super-twisting high-order sliding mode algorithm is used to control the voltage of the outer loop to obtain a given torque. Compared with the traditional PI outer loop control, the overshoot of the intermediate DC link voltage is reduced, and the voltage following ability and stability are improved. At the same time, in order to improve the utilization rate of the converter capacity of the power generation system, an improved power factor control strategy is adopted to control the motor based on vector control. Simulation experiments show that the proposed power generation system can obtain a stable and fast-recoverable intermediate DC voltage under the conditions of a wide range of internal combustion engine speed and sudden load. At the same time, the reactive power of the power generation system below the switching torque can basically stabilize near zero. After the switching torque is exceeded, the reactive power remains at a low level, which improves the utilization rate of the converter capacity.