Lidar observation network plays an important role in the research of regional distribution characteristics of particulates. The data of the lidar network in the Yangtze River Delta region were examined together with meteorological data, PM2.5 and PM10 mass concentrations and the HYSPLIT backward trajectory model, to analyze the sources and causes of particle pollution in Hangzhou and surrounding areas. The analysis showed that, the particles pollution process in September 2016 in Hangzhou was the consequence of combination of the local pollution and external transportation dust, and the coarse particles were mainly from the northwest China in the pollution process. The concentration of SO2 remained at low level, and that of PM2.5 was positively associated with the concentration of NO2, and the nitrate second particles were prevalent in fine particles. The higher concentration of NO2, high humidity, and low wind speed were all the main causes of the rapid growth of fine particles in the region.