Abstract: Social capital provides new ideas and methods for the interaction between members from different disciplinary backgrounds and heterogeneous knowledge flow in interdisciplinary research teams. However, there is a lack of research on the mechanism of social capital on knowledge integration in interdisciplinary research teams. Based on social identity theory and cooperation theory, this paper introduces team identity and task interdependence into the study of knowledge integration and analyzes the three dimensions of social capital in interdisciplinary research teams -- structural social capital, relational social capital and cognitive social capital. Taking team identification as the mediating variable and task interdependence as the moderating variable, a moderated mediating model of social capital affecting knowledge integration of interdisciplinary research teams is constructed. Based on the structural equation model analysis of a questionnaire survey of 346 members of 46 interdisciplinary research teams in a research university of C9, it is found that: structural social capital, relational social capital, and cognitive social capital have significant positive effects on team identity, and team identity has significant positive effects on the knowledge integration of interdisciplinary research teams. Team identification plays a fully mediating role in the influence of structural social capital and relational social capital on knowledge integration, and a partial mediating role in the influence of cognitive capital on knowledge integration. Task interdependence positively mediates team identity. This study contributes to the research on the influencing factors and mechanism of knowledge integration in interdisciplinary research teams and provides a theoretical basis for guiding the practice of knowledge management in interdisciplinary research teams.