Abstract: As the frequency of rock and CO2 outburst is lower than that of coal and gas outburst, although the hazards of rock and CO2 outburst are serious, the research on the mechanism of rock and CO2 outburst has not been systematic and in-depth for many years.In order to solve this problem,based on the previous research results, the CO2 genesis of the rock and coal-measure strata in the mining areas where CO2 outburst occurred in China was analyzed. Then, the characteristics of rock and CO2 outburst were summarized.The physical model of CO2 outburst was established, the process, mechanical environment and energy condition of CO2 outburst were also analyzed in this paper. The results show that the CO2 gas involved in the outburst is of inorganic origin, which is related to magmatic rock activity and coal field spontaneous combustion and pyrolysis, CO2 outburst is the result of combined effect of factors such as in-situ stress, confined gas and mechanical properties of outburst rock mass.The gas enrichment is controlled by the gas source, and the CO2 outburst danger area is distributed in dots or strips. The key structure model based on the disaster theory of coal and gas outburst key structure is consistent with the outburst site environment. The sandstone is named for Structure 1, and the rock mass supporting and wrapping the outburst sandstone is named as Structure 2, Structure 3 and Structure 4 respectively. The CO2 outburst process has gone through four stages:preparation, start-up, development and termination, and the preparation stage includes the formation of key structures until the outburst excitation is completed. The outburst start-up stage is a transient process from structure to outburst excitation. The outburst start-up is related to the energy of structure 1. Only when the accumulated energy of structure 1 is greater than the energy required for outburst, that is, the energy criterion Ce ≥ 1, can be successful started. The key structure model and energy criterion can reveal theinitiationmechanism of typical CO2 outburst accidents and provide a basis for outburst prevention and control