With the rapid development of the digital economy, entrepreneurial activities of user innovators have grown increasingly active and become an important force in stimulating nationwide entrepreneurial vitality. Although existing studies confirm that user innovator identity is a core factor affecting entrepreneurial behavior, the underlying mechanisms of identity heterogeneity remain insufficiently explored. Drawing on the social identity theory, this paper classifies user innovator identities into professional identity, community-oriented identity, and societal identity, and systematically reveals how single and multiple identities shape their entrepreneurial behavior. The results show that professional identity has a positive effect on entrepreneurial behavior, whereas community-oriented identity and societal identity have negative effects. In addition, the interaction between professional identity and community-oriented identity, as well as the interaction between professional identity and societal identity, has a positive effect on entrepreneurial behavior. Further analysis reveals that all three individual identities, as well as the two aforementioned interaction effects, influence entrepreneurial behavior through entrepreneurial opportunity recognition. Additionally, a higher level of community spanning among user innovators facilitates the translation of recognized entrepreneurial opportunities into entrepreneurial behavior. From a social identity perspective, this paper uncovers the underlying mechanisms of the transition from user innovation to user entrepreneurship, thereby enriching research on user entrepreneurship.