A superconducting magnet system with a quench protection circuit includes a superconducting magnet having a plurality of series-connected superconducting coils, a persistent current switch connected in parallel with the superconducting coils, and first and second quench protection circuits connected in parallel with the superconducting coils and the persistent current switch. The first quench protection circuit includes anti-parallel diodes and parallelly connected resistive heaters and shunt resistors, and the resistive heaters and the shunt resistors are each connected in series with the diodes. The second quench protection circuit has a diode and a metal of copper connected with the diode, and a turn-on voltage of the diode in the second quench protection circuit is lower than a turn-on voltage of the diodes in the first quench protection circuit.