Abstract: Rain-on-snow （ROS） significantly impacts ecohydrological processes on the Qinghai-Tibet Plateau, and the study of the spatiotemporal variations in ROS is crucial for water resource management in the region. In this work, the spatiotemporal variations in ROS and its driving mechanism on the Qinghai-Tibet Plateau from 1978 to 2017 were systematically analysed via daily snow depth and meteorological data from 69 stations. The results showed that ROS days in the region are mainly concentrated in October and from March to May of the following year and are distributed mainly in the eastern, central and southeastern regions. High-intensity ROS （≥50 mm/d） mostly occurred in the southeastern region in March and October and in the central region and Qilian Mountain in the northeastern part of the region in April and May. Owing to the increase in the number of rainfall days, the number of ROS days decreased significantly （P<0.01） in summer at a rate of 1.2 d/（10a） and increased slightly in spring. Moreover, influenced by the increase in the amount of rainfall, the ROS intensity decreased slightly in summer and increased significantly （P<0.05） in spring at a rate of 6 mm/（d·10a）. Continued global warming in the future could exacerbate the risk of ROS-induced flooding in the region in late winter and early spring.