Due to the characteristics of easy access, non-toxic, stable physicochemical properties and non-combustion supporting, N2 and CO2 gases attract a lot of attention of researchers as a possible substitute for SF6. Based on the gas dynamics equation, considering the collision of charged particles, the arc formation process in mixed gas circuit breaker is simulated from the microscopic point of view in this paper. According to simulation, the formation process of SF6/N2 and SF6/CO2 mixtures arc, microscopic dynamic variation of electron density and average electron energy are obtained. Mixed gases with different ratios under the same conditions are also simulated. The influence of mixed gas components on the forming process of arc is analyzed. Besides, from the micro perspective, the discharge process of SF6/N2 and SF6/CO2mixtures can be studied deeply.