This study examines the identity construction of graduate teaching volunteers in China's rural education context, focusing on the Graduate Teaching Volunteer Program in Western China. Using Dugas's Identity Triangle Model and Wenger's Communities of Practice theory as integrated frameworks, the research investigates how volunteers navigate professional identity in unfamiliar and under-resourced schools. Semi-structured interviews were conducted with twelve volunteers serving in Yunnan, Guizhou, and Shanxi provinces. Findings reveal that identity development is a dynamic process shaped by internal beliefs, social interactions, and daily pedagogical practices. While volunteers begin with strong moral motivation and civic ideals, they often encounter role ambiguity, limited institutional support, and cultural dissonance. Over time, many transition from peripheral actors to situated practitioners through adaptive strategies and relational engagement. To address these challenges, the study introduces a University-District-School (U-D-S) collaboration framework--not as a theoretical lens, but as a practical mechanism for institutional support. The model emphasizes the complementary roles of universities (pre-service preparation), local governments (policy assurance), and host schools (professional and emotional integration) in fostering identity development. By capturing the emotional tensions and transformative trajectories of volunteers, this study highlights both the challenges and potential transcendence embedded in rural teaching experiences. It contributes to global discussions on novice teacher identity, educational equity in rural areas, and volunteer service by offering theoretical insights and actionable recommendations for policy and practice.