Entrepreneurial behavior has been substantially addressed in entrepreneurship literature, but the mechanisms by which social capital influences entrepreneurial behavior among college students remain unclear, especially the potential mediating and moderating interplay among them. Therefore, drawing on social capital theory and the Stimulus-Organism-Response (S-O-R) model, this study proposed a moderated mediation model of social capital on entrepreneurial behavior. Sample data were collected via questionnaires from entrepreneurial team members participating in the Innovation and Entrepreneurship Competition in Southwest China. Results showed that (1) social capital has a positive impact on entrepreneurial behavior; (2) entrepreneurial passion partially mediates the relationship between social capital and entrepreneurial behavior; and (3) entrepreneurial risk perception positively moderates the relationship between entrepreneurial passion and behavior and thus enhances the mediating effect of entrepreneurial passion. This study provides insights into the internal mechanism of social capital on entrepreneurial behavior and also offers practical guidance for individuals, universities, and governments. The purpose of this study is to explore the impact of social capital on the entrepreneurial behavior of college students. Therefore, this study puts forward a moderated mediation framework to show how social capital stimulates entrepreneurial behavior through entrepreneurial passion and risk perception. An empirical study of 206 Chinese college students confirmed all the proposed hypotheses. The results indicate that (1) social capital has a positive impact on entrepreneurial behavior; (2) entrepreneurial passion partially mediates the relationship between social capital and entrepreneurial behavior; and (3) entrepreneurial risk perception positively moderates the relationship between entrepreneurial passion and behavior and thus enhances the mediating effect of entrepreneurial passion. Thus, this study contributes to the research of entrepreneurial behavior and relevant practical fields. However, some limitations remain. First, social capital is discussed as a whole variable so we can't explore the influence of each dimension on entrepreneurial behavior. Second, entrepreneurial passion is characterized by several boundary conditions but this study focused only on entrepreneurial risk perception as the boundary condition. Third, the use of cross-sectional data in this study limits the ability to establish causal relationships in the observed associations. Finally, this study focused on college students in Southwest China, which may affect the representativeness and universality of the results. We hope that the directions proposed in this study will inspire many colleagues to enrich our understanding of the role of social capital in stimulating entrepreneurship and innovation.