Abstract: Blowout of toxic gas diffusion from high-sulfur gas field does very great harm to the surrounding residents. Safety distance becomes an important protective measure, but it is difficult to accurately compute safety distance in complex mountain district. Through investigating a serious accident of high-sulfur blowout in China, adopting large eddy simulation method to simulate the gaseous diffusion in blowout, and calculating the accident results at different wind speed and direction, the influence of terrain on accident consequence was obtained. Through calculating the diffusion distance under different concentrations of hydrogen sulfide, an analysis and calculation method for safety distance was provided. Comprehensive analysis of the computation result show that the longest distance distributes within zonal zones. This conclusion offers a reference for safety distance standard.