Abstract: HVDC circuit breakers play a vital role in the flexible DC transmission system, among which integrated gate commutated thyristors(IGCT) is one of the key devices to ensure the normal breaking of high-voltage circuit breakers. Therefore, the study of voltage and current transient characteristics model when IGCT is turned on and off is an important content in the research of high-voltage circuit breaker system. The inherent IGCT model in PSCAD is redeveloped, and a functional model of IGCT switching off and switching off transient is established. First of all, the method of electrical equivalence and curve fitting is used to realize the different operation states of IGCT in circuit simulation. Secondly, the simulation test circuit is built in PSCAD with the proposed model and the simulation calculation under different current levels is carried out. Finally, the model is embedded into the combined DC circuit breaker respectively for simulation verification. The simulation results verify the effectiveness and correctness of the IGCT functional model, which lays the foundation for further research on the stress analysis of the semiconductor module in the high-voltage circuit breaker, and has high engineering value and research significance.