Abstract: A 3-dimentional modeling for a certain chemical factory was conducted by using Microstation software. With consideration on the important influence factors such as outside wind direction, wind speed, and different positions of ignition source, the gaseous leakage process of the poisonous, flammable and explosive vinyl chloride from the relief valve of storage tank, and the leakage, evaporation, diffusion and explosion process of the liquid vinyl chloride from the pipeline of the storage tank bottom were simulated with the software FLACS of Computational Fluid Dynamics (CFD). The simulation results show that, for the spherical tank of liquefied gases vinyl chloride at room temperature, the leakage of vinyl chloride from the relief valve of storage tank will not cause fire and explosion;but for a given liquid leakage of vinyl chloride from the pipeline, the gas cloud caused by evaporation and diffusion of vinyl chloride may cause an explosion. If there is a weak constraint condition, the explosion shock wave will be rather feeble. This study can provide precise foundation for the risk analysis, safety plan, emergency recovery and accident investigation of chemical enterprises.