Abstract: Some mathematical models were developed to forecast pollutant diffusion into atmosphere or water. Introducing the GIS (geographic information system), the models were simulated and displayed at the place where pollution hazard actually happened on the map of Shenyang City. Integrating the numerical solutions to models with GIS and analyzing the spatio-temporal diffusion of pollutants, the diffusion areas were worked out for different pollutants at different time to analyze the pollutant density and pollution intensity and what's more the important information on population and facilities near the polluted area can be acquired. Thus, it is available to forecast how heavy a pollution hazard affects the environment and nearby people especially an accidental pollution hazard, including the hazardous extent and level. Such a forecasting method lays a scientific base for emergency monitoring, field rescue and evaluation after a hazard.