The blowout accident of a natural gas well, especially, one involving poison gases such as H2S, could lead to serious consequences including casualty and property loss, and the diffusion of the sour gas from the well blowout is of great importance in the process. In this paper, a blowout accident model of sour gas well is built to simulate the blowing process. The velocity and the concentration distribution of the sour gas in the blowout accident are obtained from the numerical simulation. The velocity distribution of the blowout gas is symmetric when the gas flow is stable in air. The max velocity of the sour gas in the blowout is 875m/s in the simulation space. The safety threshold of the mass fraction of CH4 is 0.0277, and that of H2S is 7.722×10-6. The results of the simulation show that the gas blowing from well follows the law of gas jet. The safety area is the zone 100m away from the outlet of blowout well, and the danger zone is around the well because of the higher density of H2S, furthermore, the dangerous zone could be identified after blowout accident based on the simulation results.