Abstract: Based on the knowledge-based theory, this paper discusses the mechanism of how industry-university-research cooperation (IURC) and internal R&D (IRD) influence the breakthrough innovation of enterprises, and focuses on the internal and external integration mechanism in breakthrough innovation. The results show that: First of all, both IURC and IRD have an inverted U-shaped influence on breakthrough innovation, the underlying mechanism lies in their nonlinear influence on the firm’s knowledge base and the mediating effect of the knowledge base. Secondly, enterprises suffer from “NIH syndrome” in IURC, as plenty of IRD reduces the persistence and peak value of the positive effect of IURC. The internal mechanism is that IURC can improve the breadth of knowledge, while IRD will narrow the knowledge of enterprises, as a result of which, IRD makes IURC less able to promote the breadth of knowledge base. Based on the sample of China’s listed companies and patents’ information, this paper provides empirical evidence for the theoretical hypotheses, and provides new ideas for enterprises to achieve breakthrough innovation from the perspective of balancing and coordinating internal and external innovation.

Key words: industry-university-research cooperation, internal R&D, breakthrough innovation, knowledge base