Abstract: The harm of PM2.5 on human is increasing with the quick development of industry and human activities. How to reduce the harm of PM2.5 is an urgent problem. By summarizing domestic and foreign researches on PM2.5, the paper analyzed its characteristics of temporal and spatial distribution, composition and sources. Also it introduced the monitoring standards of main countries or areas in the world. Finally, the relationship of PM2.5 and vegetation was emphasized. Suitable structure vegetation could help human to prevent PM2.5 effectively, so as to reduce its harm.