Abstract: Because of complex underlying surface, low surface wind and high air humidity, which are easy to cause the accumulation of PM_2.5 in main urban area of Chongqing, Precipitation play an important role in PM_2.5 removal by the scavenging effect. Based on the meteorological observation data at Shapingba station and the hourly PM_2.5 mass concentration observation data in main urban area of Chongqing from 2015-2020, the scavenging effect of different type of rainfall processes on PM_2.5 mass concentration is analyzed. The results showed that: In the threshold analysis of PM_2.5 mass concentration in different rainfall processes, the initial mass concentration is the main influencing factor. Both rainfall processes with cold front and strong rainfall with no（weak）cold air can effectively reduce PM_2.5 mass concentration. In weak rainfall processes with no（weak）cold air, rainfall erosion and the hygroscopic growth of PM_2.5 make the PM_2.5 mass concentration change smaller. Cold front rainfall process average scavenging rate is higher than rainfall process with no（weak）cold air 1-2 grades, The average scavenging rate of rainfall process with no（weak）cold air increases with the increase of hourly maximum rainfall intensity, rainfall duration and accumulated rainfall. and the PM_2.5 mass concentration can be reduced by about 1/4 in the convective rainfall process of 3 h or more. The raindrop spectrum in the central urban area of Chongqing conforms to Gamma distribution, and there is little difference in the scavenging coefficient of aerosol particles in different spectral types of stable rainfall. The scavenging coefficient of aerosol particles in convective rainfall with maximum hourly rainfall ≥20 mm is significantly higher than that of other convective rainfall.