Coal and gas outburst is one of the most serious disasters in coal mining. In recent years, with the increasing of mining depth, the in-situ stress and gas pressure increase, and thus the coal and gas outbursts occur more and more frequently. At the same time, the in-situ stress in coal changes with mining activities; the “three zones” are formed, i.e, stress relaxation zone, stress concentration zone and original stress zone in the areas in front of the heading face and the working face, which brings more difficulties to the prevention and control of coal and gas outburst. Tianfu Sanhui No.1 mine is selected as an analysis example. The process of gas outburst is physically simulated according to the similarity theory, and the temporospatial evolution of gas pressure is discussed. It is shown that the development of outburst is a process of coal breakage in the cavity wall, which starts from the start part to the surrounding, with a relative intensity of 8.79%. Pulverized coals are thrown out intermittently and the gas pressure rise up and down in many times. The gas pressure close to the outburst mouth has a large change up to 69.2%, while it declines sharply with a short period at first then fall slowly to the atmospheric pressure far away from the outburst mouth. The isobaric surface distributes at the spherical center of outburst mouth during outburst. The gas desorption area expands outward with the shape of spherical shell and the expansion speed of spherical shell is about 130 mm/s, and the gas gradient nearby is greater.