Abstract: The negative high-voltage pulse power supply for the electron cyclotron resonance heating (ECRH) is a key support to the cyclotron’s functioning and good performance is highly required. The principle of operation was analyzed and the model was given. According to the nonlinear characteristics of tetrode and the supply’s control requirements, fuzzy control theory based on integral-separate was adopted, which combined intelligent control with power technology. Simulation results show that this system has good overshot-restrained, self-adaptive and auto-negotiating abilities using this method in comparison with PID method. This is a good new control and will be benefit to digital control intelligently.