Abstract: The C₄F₇N/CO₂ mixed gas is a potential alternative gas for SF₆. It is of great significance to further study its interruption performance in high-voltage circuit breaker for the development of new environmentally friendly power transmission methods and realization of the carbon peaking and carbon neutrality goals. Based on the magnetohydrodynamics theory, the 20 kA short-circuit current interrupting process of 40.5 kV circuit breaker filled with 0.6 MPa 5% C₄F₇N/CO₂, 10% C₄F₇N/CO₂, 15% C₄F₇N/CO₂ and pure SF₆ was calculated. The influences of C₄F₇N content on the arc temperature, arc chamber pressure and nozzle airflow characteristics were analyzed, and compared with pure SF₆. The research results show that, compared with mixed gas, SF₆ gas arc has higher arc core temperature and smaller arc radius. With the increase of C₄F₇N content, the mixed gas arc core temperature increases and the arc radius decreases. During the short-circuit interrupting process of the circuit breaker, the SF₆ gas establishes a higher gas pressure, and the airflow velocity is significantly higher than that of the mixed gas, which can form a better blowing effect to cool the arc. Finally, the arc time constant and arc power loss coefficient of different gases were calculated based on the Mary arc mathematical model, and the gas interrupting performance was quantitatively evaluated by the rate of rise of TRV (RRRV). The critical RRRV of 5% C₄F₇N/CO₂, 10% C₄F₇N/CO₂ and 15% C₄F₇N/CO₂ at 0.6 MPa are 1.54 kV/μs, 2.22 kV/μs and 2.28 kV/μs, respectively, which are much lower than 4.98 kV/μs of SF₆.