Abstract: The HIRFL-CSR dipole magnet power supply was studied. A novel scheme for designing of the synchrotron dipole magnet power supply based on the phase-controlled thyristor rectifying technology and the IGBT pulse-width modulation (PWM) converting technology was presented. After analyzing and simulating the working principle of this scheme, one complete set of prototype power supply was designed and manufactured. Through long-time on-the-spot running and testing to the prototype power supply, the current stability is <±5×10^-5/8 h, the tracking accuracy is <±2×10^-4 and the current ripple <1×10^-5. The experimental results show that this scheme can satisfy the technical requirements and indexes of the HIRFL-CSR dipole magnet to the power supply.