Abstract: In this paper, a special power supply for the grid-controlled electron gun of the multi-energy electron linac was introduced. According to the working requirement of the gridcontrolled electron gun, the cathode of the electron gun is at high voltage of -50 kV. The three outputs of the power supply, including filament power supply, bias power supply and grid-controlled pulse power supply, are respectively transmitted to the filament, cathode and grid electrode, which are all at high voltage, through the high voltage isolation transformer. The size and width of electron gun beam were adjusted accurately by computer to satisfy the requirement of the multi-energy output of the accelerator. High voltage terminal devices are all passive to reduce the failure rate. The power supply with simple structure, convenient adjustment and stable operation, has been normally working continuously on the multi-energy electron linac for nearly four years.