Abstract: C₄F₇N/CO₂ gas 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/CO₂ gas 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 low-temperature（＞8 kK） region. The radial thermal convection capacity of C₄F₇N gas mixture is weaker than that of SF₆ at temperatures less than 5 kK and is positively correlated with the concentration of O₂ in low-temperature（greater than 8 kK） region.