Abstract: In order to study the dynamic process of the coal and gas outburst, a true triaxial coal and gas outburst simulation test system was applied to conduct th e simulation test of the coal and gas outburst under different condition, dynamically monitor and measure the stress and gas pressure variation features in the outburst process and statitically analyze the distribution features of the threw coal. The results showed that there was a gas pressure threshold value existed that the outburst occurred or not. When the gas pressure was higher than the threshold value, the outburst strength would be increased with the gas pressure increased. The outburst ho le would have a small mouth and a big chamber in a pear shape and the coal behind the hole more closed to the outburst bole would be in a higher broken degree. The threw coal on the horizontal ground would be in a shutle shape stripe distribution, would be small particle fine coal mainly and would be concentrated at an area far fro m the outburst outlet. With the gas pressure increased, the broken effect of the thrown coal would be more remarkable. The coal and gas outburst would be a dynamic process of the rapid development and could be divided into five stages of inoculation, excitation, development, termination and throwing.