Abstract:C4F7N/CO2gas mixture is one of SF6 alternative gases, but it still exists solid carbon precipitation problems in interrupting large capacity short circuit current. The researches show that the addition of O2 can effectively inhibit the generation of solid carbon, and at the same time can effectively increase the pressure of arc-extinguishing chamber to improve the arc extinguishing performance of gas. In order to further study the effect of O2 on energy dissipation of arc of gas mixture, the particle size compostion of arc plasma of C4F7N/CO2gas mixture with different content of O2 is calculated based on Gibbs free energy minimization principle under the assumption of local thermodynamic equilibrium conditions, the thermodynamic properties of the gases with different mixing ratios are obtained by standard statistical thermophysics calculation methods, and the effects of different contents and pressures of O2 on thermodynamic properties of arc plasma of gas mixture are analyzed comparatively. The results show that O2 inhibits the generation of CO in low-temperature region, which leads to some differences in thermodynamic properties of gas mixture with different contents of O2. The axial thermal convection capacity of C4F7N gas mixture is larger than that of SF6, and is positively correlated with the concentration of O2 in lowtemperature (＞8 kK) region. The radial thermal convection capacity of C4F7N gas mixture is weaker than that of SF6at temperatures less than 5 kK and is positively correlated with the concentration of O2 in lowtemperature (greater than 8 kK) region.