Abstract: Basing on the measurement of in-situ stress,mechanical property of coal and gas pressure,finite element analysis software of Ansys and Flac^3D are used to simulate the '6.20′ outsized outburst mechanical process of Hongling coal mine.The three stages of stress including stress accumulate before outburst,coal cracking by stress inducement,coal outburst by gas pressure are expatiated.The numerical results demonstrate the process of the outburst from the crack initiation,propagation,breakage,mass outburst and stopped,and the numerical analysis results are consistent with actual measurement outcome.It can offer academic guidance for engineering design and the further depth exploitation.