The Tangjiawan three-terminal flexible DC distribution network project successfully applied the world's first ±10 kV three-port hybrid DC circuit breaker，which can realize the connection of multi-terminal converter stations and rapid fault isolation，thus ensuring the safe and reliable operation of the system. the RTDS simulation system is designed for the topology of the three-port hybrid DC circuit breaker in the Tangjiawan three-terminal flexible DC distribution network project in Zhuhai，combined with the control and protection FPT test requirements of the DC transmission project to design the external interface，and finally based on the hybrid DC circuit breaker breaking strategy，the Path2 hybrid DC circuit breaker breaking logic and commutation process in the three-port hybrid DC circuit breaker are simulated and verified. The simulation test results show that the RTDS simulation system can break the fault current of 2 kA within 3 ms. At present，the three-port hybrid DC circuit breaker RTDS simulation system is connected to the Tangjiawan three-terminal flexible DC distribution network project （physical layer） control and protection RTDS test system.