Abstract: Using the self-developed “coal and gas outburst simulation device”, we conducted three-dimensional loading simulation experiments of coal and gas outburst for different initial gas pressure and outburst mouth thickness and different diameters of coal samples. The results show that: under the condition of lower coalbed methane pressure, coal and gas outburst will occur if there exists larger external loading, lower coal uncovering thickness and larger roadway section. There is a critical value of outburst mouth thickness during the whole coal and gas outburst process, and changing the value can change coal and gas outburst and outburst intensity. The roadway section has some effect on outburst phenomenon, coal and gas outburst is effectively prevented through reducing section. Followed by the increased intensity of outburst, the quality of coal powders and cast distances are increased. And then most of coal and gas outburst accidents occurred at the most outburst intensity.