Abstract: In recent years, the environmentally friendly insulating medium C₄F₇N/CO₂ mixed gas has attracted wide attention due to its excellent electrical performance and environmental protection advantages, which has the potential to replace SF₆ gas. In this paper, the decomposition experiments of C₄F₇N/CO₂ mixture under partial discharge, partial overheating and spark discharge were carried out according to the fault conditions that may be encountered in actual operation. The decomposition products under different working conditions were qualitatively analyzed by gas chromatography-mass spectrometry (GC-MS), and the characteristic decomposition products under different working conditions were proposed. The results show that the decomposition products under three different conditions are mainly composed of saturated fluorocarbons (CF₄, C₂F₆, C₃F₈, C₄F₁₀), unsaturated fluorocarbons (C₂F₄, C₃F₆, C₄F₈, i-C₄F₈) and nitrogenous compounds (C₂F₃N, C₃F₅N, C₂N₂, HCN). According to the difference of decomposition products under different working conditions, HCN and peak area(C₃F₈)/peak area(C₂F₃N) > 1 can be used as the characteristic decomposition products under partial discharge condition.C₄F₈ and its isomer i-C₄F₈ are used as characteristic decomposition products under partial overheating condition. Under the condition of spark discharge, CF₄ and peak area(C₃F₈)/peak area(C₂F₃N) < 1 are taken as the characteristic decomposition products of spark discharge. Characteristic decomposition products of power frequency breakdown are C₄F₆ and C₃F₃N.