<p>In major sports events, university volunteers play a crucial role. Therefore, exploring the motivation behind their participation is vital for effectively recruiting, managing, and retaining volunteer resources. Given that current qualitative research on the motivation of university student volunteers is primarily grounded in Western cultural contexts, this study aims to fill the research gap from an Eastern cultural perspective. We selected the 19th Hangzhou Asian Games as a case study to delve into the intrinsic logic and mechanism of volunteer service motivation within the backdrop of Chinese culture and values. Through one-on-one semi-structured interviews with 43 university students who applied to be volunteers for the Hangzhou Asian Games, this study employed a systematic Grounded Theory analysis to deconstruct the factors influencing volunteer motivation and developed a multi-dimensional framework for volunteer motivation. This framework includes aspects of social value, personal reward, interest orientation, behavior planning, and volunteer identity, elucidating the internal logic behind university students’ volunteer motivations across three dimensions: internal driving feedback factors, external driving value factors, and planned behavior factors. Furthermore, the study analyzed the core mechanism of university student volunteers’ motivation from the perspectives of respect, social contact, and self-fulfillment needs. Based on an in-depth discussion of volunteer motivation, this paper provides suggestions for universities and event organizers in the recruitment and retention of volunteers. The novelty of this research lies in integrating the analysis of volunteer motivation into the context of Chinese culture, offering a framework and strategies for volunteer management based on an understanding of local culture.</p>