SF6, the most widely used electrical-equipment-insulation gas, has serious greenhouse effects. C5F10O has attracted much attention as an alternative gas in recent two years, but the environmental impact of its decomposition products is unclear. In this work, the decomposition characteristics of C5F10O were studied based on gas chromatography-mass spectrometry and density functional theory. We found that the amount of decomposition products of C5F10O, namely, CF4, C2F6, C3F6, C3F8, C4F10, and C6F14, increased with increased number of discharges. Under a high-energy electric field, the C-C bond of C5F10O between carbonyl carbon and α-carbon atoms was most likely to break and generate CF3CO•, C3F7• or C3F7CO•, CF3• free radicals. CF3•, and C3F7• free radicals produced by the breakage more easily recombined to form small molecular products. By analyzing the ionization parameters, toxicity, and environmental effects of C5F10O and its decomposition products, we found that C5F10O gas mixtures exhibit great decomposition and environmental characteristics with low toxicity, with great potential to replace SF6.