Abstract: In magnetic confinement fusion devices, the quench protection system (QPS) uses DC circuit breaker to quickly interrupt the superconducting magnet current to realize the transfer and release of the magnet energy to ensure its safety. With the continuous upgrade of the superconducting magnet operating current level, the design of DC circuit breaker faces great challenges. In accordance with the 10 kV/100 kA high capacity QPS design, it is proposed that a DC vacuum circuit breaker (VCB) is used as the main protection switch for interrupting 100 kA superconducting magnet current, and its breaking and commutation process is analyzed in detail. Firstly, the topology and working principle of QPS are introduced. Then, the mathematical equations of VCB in the breaking and commutation process are analyzed. Based on the breaking reliability theory of VCB, the calculation and parameter design of the commutation circuit, the energy discharge circuit, and the snubber circuit are carried out, respectively. Finally, the 100 kA DC current breaking experiments are carried out. The study results show that using DC VCB to interrupt the 100 kA magnet current in QPS has theoretical and engineering feasibility, and the experiment verifies that the designed VCB prototype can effectively break 100 kA current, and the commutation process is in line with the expected judgment. The study in this paper provides technical supports for the design of DC circuit breaker in high-power QPS.