Abstract: Based on the accident scene of the major coal and gas outburst in Puding County of Guizhou province in May 16th 2012, combined with the accident characteristics, outburst mechanism and outburst energy dynamic balance theory, the analysis shows that the subjective factors of the major outburst accident are failed to take measures against outburst when M₂ coal seam was drived. Informal tunnel mining method caused the stress concentration, and the tunneling face blasting induced the coal and gas outburst without taking safety protection measures. The accident point of M₂ coal seam becomes thickened soft, ground stress increases and high gas pressure gradient is the objective factors of the accident. Before the accident, 2151 tunneling face outburst power increases, consumption power goes down, the outburst power is more than the consume power, leading to outburst for the loss of balance in the dynamic process. The main reason causing casualties is countercurrent gas, which resultes in a large number of gas emission in a short time and coal thrown down and blocked the ventilation down laneway in outburst location.