Based on the daily precipitation data of 269 meteorological observation stations in the south area of West China from 1971 to 2017 and the NCEP/NCAR reanalysis data, etc., the change of autumn rain intensity and the characteristics of corresponding atmospheric circulation anomalies in the south area of West China were analyzed, the key area of atmospheric cold source over the Tibetan Plateau affecting autumn rain was sought, and the influences of atmospheric cold source in the key area on autumn rain intensity in the south area of West China were diagnosed. The results show that the intensity of autumn rain in the south area of West China hadn’t a significant change trend as a whole, and its interannual change might be affected by the hysteresis of anomalous changes of atmospheric cold source over the Tibetan Plateau in previous winter (January). When the atmospheric cold source over the Tibetan Plateau was abnormally strong (weak) in previous winter, it could stimulate the cyclonic (anti-cyclonic) anomalous circulation from the South China Sea to the western Pacific and maintain until summer. The continuous westward (eastward) airflow on the south side of the cyclone (anti-cyclone) caused surface warm water over the western (central) Pacific to travel eastward (westward), which caused anomalous warm (cold) of sea temperature in the equatorial central Pacific, then stimulate a cyclonic (anti-cyclonic) circulation in the western Pacific region. The water vapor conditions were poor (good) in the south area of West China under the control of northerly (southerly) winds in the west side of the cyclone (anti-cyclone), the precipitation was less (more), and autumn rain was weak (strong).