Abstract: Through coal and gas outburst simulation experiments, we studied gas pressure change law and gas destructive effect in the process of coal and gas outburst. Research shows that stress and gas pressure can cause coal and gas outburst when they reach a certain gradient and the outburst obviously lags the pressure relief process; the change of gas pressure has obvious regularity in the process of coal and gas outburst, gas pressure change form suddenly drops, after rapid rises and fluctuates, reaches peak and then gradually decreases, the change of gas pressure form and the outburst development evolution process has a good correspondence; gas pressure changes in the process of extrusion and outburst have significant differences. Coal under the action of stress and gas pressure difference, shear and tensile failure happens, spallation failure characteristics of coal near the discharge pressure is obvious.