This paper calculated the electric field and flow field on 40.5 kV SF6 circuit breaker, established non-equilibrium arc energy model on the basis of gas macro parameters, calculated pressure, density and temperature distribution in the Arcing chamber under the condition of light and the capacitor open circuit. Analysis the circuit breaker pressure characteristics in the process of opening circuit, extinguishing the dielectric recovery characteristic curve between arc contact obtained by electric field and flow field coupling calculation. The results show that: When opening small capacitive current in the circuit breaker, if open circuit phase angle respectively 1/10π, 1/5π, 3/10π, 1/5π, 1/2π, the corresponding arc total duration of 0.6ms, 0.73ms, 1.8ms, 2.9ms and 3.7ms, arc extinguished in advance. After arc extinguished, the breakdown voltage is higher than that of transient recovery voltage value consistently, can open circuit arc and not renewed successfully.