With the advent of knowledge economy, enterprises are relying on knowledge integration, while firm-internal social capital takes an important role in knowledge integration and core competence. The sample of this study derived from Beijing and Guangzhou city, we want to explore whether and how internal social capital influence on knowledge integration and core competence. And finally, we proofed that internal social capital have a direct impact on core competence, while knowledge integration took a partial mediation role between them. In practice, these conclusions also provide important guidance for firms to effectively build their core competence.