The constant power excitation control system of a internal combustion locomotive is a nonlinear time-varying system. In the control of this nonlinear time-varying system using the traditional PID control algorithm, its dynamic response and static characteristics cannot be taken into consideration at the same time when the system parameters change with time. The traditional PID control algorithm has limitations in control performance in these cases. In order to improve the stability and dynamic response performance of the constant power excitation control system of a internal combustion locomotive, this paper takes the constant power excitation system of a certain type of internal combustion locomotive as the research object and combines fuzzy control theory and methods to design a fuzzy controller. The fuzzy controller uses fuzzy The method combines the basic control algorithm with the incremental control algorithm, and the fuzzy controller was tested and verified, and the test results were compared with the control results of the traditional PID controller. The results show that the fuzzy controller exhibits better control performance than the traditional PID controller.