Abstract: Grounded in capacity building theory and social ecosystem theory, this study adopted a case study approach, focusing on the capacity building of mediators in H Village, a mountainous area in Yunnan Province. Through participatory observation, in-depth interviews, and quantitative assessment, the study explored the enhancement of mediators’ competencies through group work intervention and proposes pathways for optimizing the mediation ecosystem. The findings revealed the following: on the one hand, group work, through interactive learning and continuous follow-up, could effectively improve mediators’ cognitive abilities, knowledge base, and professional skills; on the other hand, the synergistic optimization of the social ecosystem could provide long-term support for the capacity building of rural mediators. This paper contributed to the empirical research on rural mediator capacity building by integrating capacity building theory and social ecosystem theory, offering both theoretical insights and practical models for grassroots mediator development, which held practical significance for improving mechanisms for conflict resolution in rural areas.