Abstract: Neutral beam injection (NBI) is one of the most effective ways to heat plasma in Tokamak. The arc discharge ion source of NBI on HL-2A Tokamak is the bucket cusped multiple magnetic field ion source. According to the characteristics of the ion source and requirements of system, the technical design of the arc power supply was expounded from several aspects of its function, main circuit topology, control hardware circuits and control sequence. The apparatus includes phase-shifted AC low-voltage regulator, high-voltage isolated step-down transformer, and rectifier with an output filter and the notch circuit. IGBT in series dummy resistance load and parallel with ion source was implemented in the notch circuit, and it can shift the current instantaneously single or multiple times to make the NBI system operating safety in the process of intense current ion beam extraction or to protect arcing in grids. The low-level-voltage and the high-level-voltage controller adopted the high performance digital signal processor and complex programmable logic device. The experimental waveforms prove that the maximum output capacity specification of the arc power supply is 200 kW/1 000 A, ripple is less than 2%, turn off time can achieve several microseconds. The arc power supply has operated safely for three years, and it meets the requirements of the system and the ion source device.