Abstract: The study of drought risk transmission and its driving factors is of great significance for drought early warning and water resources management. We use the standardized precipitation index to analyze the drought characteristics of different time scales in Southwest China. Three risk factors, vulnerability, exposure and resilience, are used to assess regional comprehensive drought risk; And the characteristics and driving factors of drought risk transmission are examined using a Markov chain and random forest algorithm. The results show the spatial patterns of drought duration and severity are roughly the same in different time scales. The order of high to low drought risk in Southwest China is Sichuan, Chongqing, Yunnan, Guangxi, and Guizhou provinces. If an area is adjacent to a low-risk one, its drought risk level will decrease at a relatively high probability, and vice versa. East Asian Summer Monsoon Index and Atlantic Multidecadal Oscillation are the key factors causing the drought in Chongqing, Sichuan, Yunnan, and Guangxi, while Atlantic Multidecadal Oscillation and Pacific Decadal Oscillation are the main causes of drought in Guizhou.

Key words: standardized precipitation index, drought risk, Markov chain, risk transmission, random forest algorithm, Southwest China