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SF₆/CF₄ mixture is considered a potential substitution for SF₆ in gas-insulated equipment owing to the considerable insulation and low temperature characteristics of CF₄. This paper concerns the substitutability of the mixture on the surface flashover property. Epoxy resin composites for solid insulators are applied since flashover at the insulator interface often occurs and results in severe damage to the safe operation of the equipment. Two kinds of electrode systems are designed to study DC flashover properties with different electric field uniformities. The obtained result shows that the flashover voltage in the 20% SF₆/80% CF₄ mixture achieved more than 70% of the voltage in SF₆ at the same pressure. The mixture shows considerable synergy in the surface flashover process and performed different tendencies with varying gas pressures and contents under different electrode systems due to the influence of surface accumulated charge. Moreover, it is considered that surface charge due to ionization may result in a reversal phenomenon for voltage polarity with increasing pressure. The results indicate the possibility of SF₆/CF₄ functioning as an efficient substitution of SF₆ with a considerable insulation property and improved environmental protection characteristics.