Abstract: Based on the reanalysis data provided by the National Centers for Environmental Prediction/National Center for Atmospheric Research, European Centre for Medium-Range Weather Forecasts, and Sichuan meteorological stations, the climatic characteristics of haze weather over the Sichuan Basin in winter, its corresponding key circulation system, and its response to the thermal action of the Tibet Plateau in the early stage were analyzed through linear correlation and synthetic analyses. The findings showed that the increase in the number of seasonal haze days in the Sichuan Basin is negligible, and the three major urban agglomerations in the Sichuan Basin are prone to haze in winter. During the haze days in the Sichuan Basin in winter, the critical circulation systems are positive anomalies of geopotential heights at 850, 500, and 200 hPa; abnormal subsidence movement; and abnormally weak Siberian high. Under such circumstances, the lower troposphere over the Sichuan Basin is dominated by anomalous northwest winds, in situ stable stratification can be easily set up, boundary layer height is lower than normal, and surface relative humidity is reduced. The thermal effect in the key areas of the Tibet Plateau in early November is an important external forcing factor that affects the frequent occurrence of haze weather during winter in the Sichuan Basin. During the winter of low–heat index years in the key areas of the plateau in early November, the Aleutian Low and Siberian High are significantly weak; there is a bow wave train similar to the South Branch Trough wave train system from the North Atlantic to the Northwest Pacific. Further, the Tibet Plateau is characterized by significant positive geopotential height anomaly, and the Sichuan Basin is characterized by anticyclone circulation combined with an abnormal downdraft, which is conducive to haze formation. The atmospheric heat source anomaly over the Tibet Plateau and the haze day anomaly in the Sichuan Basin may result from the propagation of disturbances in the upstream wave train, especially in the mid-latitude North Atlantic. In addition, the east side of the “leeward slope” of the Tibet Plateau is affected by the downdraft, increasing the number of haze days.