Abstract: Due to the serious greenhouse effect of SF₆ gas,which is currently widely used in the electrical power industry,it has become a common view that an environmental-friendly alternative candidate of excellent insulation performance should be found to replace SF₆.Recently,the C₃F₇CN and its mixture,which have a low global warming potential（GWP）and excellent insulation properties,have attracted wide attention from domestic and foreign scholars.There are few studies on its decomposition mechanism under discharge.In this paper,firstly based on the molecular dynamics method and the ReaxFF force field and the density functional theory,the decomposition mechanism of C₃F₇CN/CO₂ gas mixture was simulated from the micro level.Based on the constructed C₃F₇CN/CO₂ models,the effect of temperature on the decomposition process of C₃F₇CN was studied,and the possible decomposition paths,product types and distributions were analyzed.The results show that the decomposition of C₃F₇CN can easily generate various kinds of free radicals such as CF₃?,C₃F₇?,C?,CF₃CFCN?,CF₂,F?and so on under the conditions of local overheating or discharge,and further reactive combination of these free radicals will generate products such as CF₄,C₂F₆,C₃F₈,CF₃CN,CO and so on.Then,based on the gas insulation test platform and the gas chromatography mass spectrometer（GC-MS）,the products after multiple breakdowns were analyzed.The test results show that the decomposition product are mainly CF₄,C₂F₆,CF₃CN.These molecules products have good insulation ability,which insure the insulation performance of C₃F₇CN/CO₂ gas mixture.The conclusions provide theoretical basis for further research of insulation properties and synergistic effect of C₃F₇CN/CO₂ gas mixture,and guide its practical engineering application.