Abstract: Based on the Land Surface Data Assimilation System (CLDAS) data of China Meteorological Administration from January 2018 to December 2020, the height of atmospheric mixed layer in Sichuan province was calculated by Roche method, and its spatial and temporal distribution characteristics were analyzed. The relationship between the height change of atmospheric mixed layer and air quality was further analyzed by combining with the air quality monitoring data of atmospheric environment. The results show that:The height distribution of atmospheric mixed layer in Sichuan province is high in the west and low in the east. There is a significant difference between the Basin Area and Panxi Area and the Chuanxi Plateau in the seasonal variation of the atmospheric mixed layer height. In Sichuan Basin,the height is the highest in spring and the lowest in autumn,while in the Western Sichuan Plateau and Panxi area, the height is the highest in autumn and the lowest in summer. The monthly and daily variation trends of the atmospheric mixed layer height in all areas of Sichuan province are basically the same. The atmospheric mixed layer height in Sichuan province is significantly positively correlated with O₃ mass concentration and negatively correlated with PM_2.5 mass concentration.