Abstract:China is a mountainous country, with hills, mountains, and plateaus cover about two-thirds of its total land area. The vast area, huge population, rich natural resources, and great potential of development in mountain areas make them the most important “rear garden” supporting the sustainable development of the whole country. Nevertheless, China’s mountain areas are also prone to various kinds of natural disasters, and thus formed a scenario of high overlap between the high-risk zone of natural disasters and the lagging zone of social and economic development. And such scenario has caused significant waste of various related inputs, and becoming a key obstacle to the goal of modernization for mountain areas in sync with other regions by 2035. Based on a systematic analysis of main challenges faced by disaster risk reduction and green development in mountain areas, the study innovates the “Disaster –Environment–Human” green synergy theory based on the human and environment harmonization theory. After that, a novel synergy mode of disaster risk reduction and green development is proposed, and its synergy mechanisms, main synergy paths, and various synergy technologies are analyzed. The synergy theory and mode were applied in a demonstration zone named Reshui River basin located in Xide County, Liangshan Yi Autonomous Prefecture, Sichuan Province, the first demonstration zone of the synergy mode of disaster risk reduction and green development in China. Finally, the feasibility and the specific paths of promoting the synergism mode are analyzed in mountain areas nationwide. This study can not only guide the consolidation of poverty alleviation achievements, promote the practice of rural revitalization strategy, but also help to improve the capability of comprehensive governance and promote the modernization progress in mountain areas of China.