Based on daily data from 97 stations in Southwest China (SWC) from 1960 to 2009, we calculated the dry-wet index, which considers precipitation and temperature, and studied the spatiotemporal variations of the autumn dry-wet index. Using the similarity method, a composite similar index was introduced and the distribution of dry-wet conditions was classified according to this index. The main types of atmospheric circulation characteristics in anomalous years are discussed using the NCEP/NCAR reanalysis data. The results suggest that the drying trend is significant in SWC. There are three main modes of autumn dry-wet variations in SWC: consistent across the whole region, a dipole in the latitudinal direction, and a dipole in the longitudinal direction. The distribution of dry-wet conditions can be divided into seven types: the consistent dry (A-), the consistent wet (A+), eastern wet-western dry (B-), eastern dry-western wet (B+), southern wet-northern dry (C-), southern dry-northern wet (C+), and atypical (D). The A (including A- and A+) type is the most frequent (no less than 50%); the B (including B- and B+) type is second (about 25%); the C (including C- and C+) type is less frequent (about 15%); and the D type occurs few times (less than 10%). From October to November, the eastern wet areas have a good chance to expand and cover the whole area in the next month (no less than 50%). The A type is mainly affected by anomalies of the East Asia major trough, the circulation over the South China Sea, and the configuration between the western Pacific subtropical high and South Asia high. The B type anomaly correlates with the vertical movement anomalies in the western-eastern SWC and the wind anomalies in eastern SWC.