Mountainous agriculture supports 15% of the global population, but its sustainability is facing challenges with the social transition. Honghe Hani Rice Terrace System (HHRTS), China, a double world‐level heritage, performs strong resilience to challenges. Available studies on HHRTS examines its sustainability from some perspectives but lack a systemic elaboration on its sustainable mechanism. This study extensively examines the literature on HHRTS and offers a comprehensive analysis of its sustainability. The findings suggest that mountainous agricultural sustainability depends on the support from relatively enough water and land resources and diverse employment based on these resources (economic sustainability), the environmental stability based on reasonable landscape structure, rich biodiversity and ecological farming methods (environmental sustainability), and social stability based on the well‐developing social structure, efficient management system, and relevant cultural restraint and guidance (social sustainability) as well as the dynamic interaction among the three dimensions. Among them, traditional knowledge and cultures play a positive role in maintaining the stability of terraced landscapes, but their role is weakening with industrialization and urbanization. This study provides a systemic explanation of a dynamic evolution mechanism that the economic and social factors drive local people to maintain a mountainous agricultural system from the agricultural society to the industrial society based on the theory of planned behavior. This study also provides abundant local knowledge, experiences, and an analytical framework for reconstructing a sustainable mountainous agricultural system in the socio‐economic transformation stage.