Abstract: Based on the analysis of radar echo evolution and circulation variations during the hail disasters occurring over Zhaotong, Qujing, Kunming, and Yuxi on August 10—11, 2023, this study investigated the radar echo characteristics and formation mechanisms of the hail process. The main conclusions are as follows: (1) The radar echoes of the hail process exhibited features such as human-shaped echoes, squall lines, bow echoes, hook echoes and V-shaped notches. Local convective cells merged with adjacent supercells to expand the echo coverage. The Vertical Integrated Liquid Water (VIL) value nearly doubled 30 minutes prior to hail occurrence, showing a positive correlation with hail intensity. Low-level radial velocity exceeded 10 m/s, with significant updrafts. Remarkable vertical wind variations indicated intense vertical wind shear. (2) The hail process occurred after the landing of Tropical Cyclone Khanun. The westerly belt reorganized into a two-trough and one-ridge pattern at upper levels. The eastward-slowing upper trough transported cold air southward to northern Yunnan, which converged with warm and moist air carried by the low-level jet from the southern ocean, creating a strongly unstable stratification. The slow eastward movement of the South Asian High enhanced upper-level divergence, and southeastern Yunnan was located in the convergence, shear and positive vorticity zone ahead and to the left of the jet axis. The coupled upper-level divergence and low-level convergence produced robust updrafts. (3) Prior to hail initiation, the T-Td value was less than 3 ℃ below 640 hPa, with a steep vertical humidity gradient. The layer from 600 hPa to 700 hPa was the major unstable energy accumulation layer. Strong vertical wind shear increased atmospheric instability and favored convective maintenance.