Abstract: The meteorological conditions of a persistent polluted weather process in Chengdu from December 18,2017 to January 2,2018 are analyzed by using meteorological station data and NCEP reanalysis data.The results show that the pollution process is a moderate to severe pollution event.The circulation situation of 500 hPa and its adjustment are closely related to the development of this pollution situation.The subsidence inversion layer and isothermal layer associated with 500hPa high pressure ridge are the main factors leading to the pollution process.With the adjustment of circulation,the low trough moved eastward,the pollution situation was improved,and finally the pollution process ended.In the process of polluted weather,the surface inversion and stable atmosphere restrained the diffusion of pollutants,but did not play a leading role in the generation and evolution of polluted weather.In addition,there are cold air entering the basin for four times.The cold air mainly comes from the north and east of Sichuan Basin,which alleviates the pollution,but does not play a decisive role in the end of the pollution process.