Abstract: Multi-campus education has become more common in Chinese universities． However, campus dispersion often constrains inter-campus collaboration among graduates with fragmented cooperation, weak social support, and scattered faculty resources． In this study data were collected from graduate students in geography on the Beijing campus and the Zhuhai campus of Beijing Normal University by questionnaires and semi-structured interviews． Social network analysis and QAP regression showed that the overall inter-campus collaboration network is loosely connected, with strong intra-disciplinary clustering but limited inter-disciplinary cooperation． Significant differences exist in centrality of disciplines within the network． Zhuhai Natural Disaster Studies has the widest collaboration, while Zhuhai Physical Geography and Beijing Natural Disaster Studies act as key bridges． Collaboration is shaped by multiple factors: non-academic interactions are crucial, distance can spur willingness, yet enthusiasm often fails to become actual cooperation． This study develops an analytical framework of structures and mechanisms of inter-campus collaboration, and offers theoretical insights and practical reference for improving graduate student collaboration management in multi-campus universities．