Abstract: In view of the characteristics of APU with the parameters discreteness,the nonlinearity and uncertainty,a new type speed control system of APU based on the theory of fuzzy control was developed in this paper,to ensure the running of gasoline engine in APU to be economic and with high efficiency.The structure and working principle of the fuzzy controller were described,and the design procedure of the fuzzy controller was given in detail.The experimental results show that the step response of the speed is small in the overshoot,little in the fluctuation range and the regulation time.This control system has not only achieved the purpose of speed control of APU but also has good quality.The results are validated by road tests,and show that the fuzzy controller can guarantee the engine is running in the economic region,while ensure the efficiency of generator.The desired purpose and effect of control system can be achieved.