Abstract: Through big sand storm cases in the western region in China in last 15 years, the effects of sand storm on the air environmental background value in Gansu province were investigated and analyzed. Using air dustfall data and samples at background sites, the quantity of dustfall, distribution scope, chemical composition and grain distribution characteristics, etc. of sand storm deposition at different areas were analyzed. It is found that sand storm is much more than a kind of special disastrous weather; it is also a kind of air pollution phenomenon covering different provinces. In case of no wet deposition opportunities, it can be transported to far away places, thus affecting and polluting large area. Sand storm can transport some hazardous matters to the downwind and leave potential and long effects on the ecological environment. The sand storm dustfall in Gansu is distributed with the core at the east of Hexi Corridor, disperses to the downwind areas, forming gradient distribution from the west to the southeast. Because of the influence of sand storm, the overall level of air environmental background value of dustfall is increasing in Gansu province in the last 15 years.