Abstract: The extreme dry season torrential rain process that occurred on January 9, 2015 over Yunnan Province was explored based on the NCEP reanalysis data, the conventional and unconventional observation data. The results showed that this process was caused by a deep Southern Branch Trough over the middle of the Bay of Bengal, the shear line on 700 hPa and the cold front on ground. The strong MJO was during the “wet window” period, which was also an indicator for the water vapor transport and the development of convection. During that process, the southwest low-level jet in front of the Southern Branch Trough provided abundant water vapor. The rainstorm area was basically consistent with strong vapor convergence area. Under the coupling of the high-level and low-level jets, the ascending branch of secondary circulation forced by the high-level jet affected Yunnan Province. The uplift of the cold front, and the ascending branches of secondary circulations forced by the cold front and the jet, led to the enhancement of updraft. The unstable energy transported by the southwest low-level jet led to such convective weather: the rainstorm area in Southwest Yunnan was dominated by strong convective weather, while the rainstorm area in central Yunnan was dominated by stable precipitation. Obviously, the comprehensive analysis by taking atmospheric stability into account was helpful to judge the location of severe convective weather over Yunnan Province in the dry season.