According to the environmental bulletin in recent years, PM2.5 has been one of the primary pollutants of air pollution in China. And researches about PM2.5 in source analysis, composition, physical and chemical properties, prediction and other aspects have been studied. In order to better figure out the current research status of PM2.5 in China, this paper analyzes these related studies from the qualitative and quantitative aspects. From the qualitative aspect, the paper analyzes the composition and source of PM2.5. From the quantitative aspect, the paper describes the prediction method of PM2.5 concentration from two aspects, one is based on ground observation stations, the other is based on satellite data. Whether from a qualitative or quantitative perspective, the research on PM2.5 is still very necessary. The control of air pollution has a long way to go, and continuous research and practice are still required.