Abstract: Through the statistics of PM_2.5data of Suqian in the autumn and winter of 2017-2021 and the conventional meteorological observation data of the same period,based on the daily variation characteristics of PM_2.5,it is divided into three processes:rapid accumulation,slow accumulation and dissipation according to the concentration change from 15:00 to 23:00. The accumulation characteristics of PM_2.5in Suqian are analyzed from the perspective of the accumulation rate.It is also applied to study the correlation between circulation situation and accumulation rate under the process of heavy pollution weather.The results show that the average accumulation rate of PM_2.5in the rapid accumulation process is 7.14 μg·m^-3·h^-1;the average accumulation rate of PM_2.5in the slow accumulation process is 3.27 μg·m^-3·h^-1;the average dissipation rate of PM_2.5in the dissipation process is 5.42 μg·m^-3·h^-1.The slow accumulation of PM_2.5is characterized by high temperature,high wind speed,low humidity and weak inversion intensity,while the rapid accumulation is the opposite.The potential source areas of PM_2.5during the slow accumulation process are mainly located in northern Jiangsu,Shandong and Hebei,while the main potential source areas of PM_2.5during the fast accumulation process are mainly located in Anhui and Hubei.The fast accumulation process is dominated by the high altitude trough followed by the ground high-pressure front,and the slow accumulation process is dominated by the latitudinal circulation with the homogeneity surface pressure field.