In order to study the influence of the arc contact ablation degree on the multi-physical field changes in the arc extinguishing chamber during the breaking process of the SF6 circuit breaker, it is established multi- physical field coupling simulation models of breaking process in arc extinguishing chamber that the arc contact stroke is reduced by 0, 5 mm, 10 mm and 15 mm. The multi-physics coupling simulation model of the process obtains the temperature, airflow and electric field distribution characteristics in the arc extinguishing chamber during the short-circuit current interruption process. The calculation results show that, during the breaking process, the highest temperature of the arc appears at the arc root, and its value changes little with the degree of ablation of the arc contact; with the increase of arc contact ablation, the maximum velocity of SF6 gas decreases and the arc blowing effect decreases; the maximum field strength is concentrated at the end of the static arc contact or the arc corner of the moving arc contact, and the distortion becomes serious with the ablation of the arc contact. On this basis, according to the gas breakdown criterion of the streamer theory, the recovery characteristics of the SF6 medium under different arc contact ablation levels are calculated, and it is found that when the arc contact stroke is reduced by 15 mm, the critical breakdown voltage is lower than the transient recovery voltage, the contact gap may break down again and cause the arc to reignite. The research results can provide theoretical support for the degradation mechanism of the electrical life of SF6 circuit breakers.