Abstract:Open innovation is an important channel for firm to obtain external tacit knowledge and expand social capital ,which is of great significance for enterprises to improve their breakthrough innovation ability to implement breakthrough innovation more effectively. This paper has a theoretical analysis and empirical research on high-tech enterprises in the Yangtze River Delta, the following conclusions can be concluded: (1) Open innovation has significant positive impact on abilities of skill-based tacit knowledge acquisition, cognitive tacit knowledge acquisition and enterprise breakthrough innovation. (2) Skill-based tacit knowledge acquisition has significant positive impact on the company"s breakthrough innovation ability, while cognitive tacit knowledge acquisition has significant positive impact on the firm"s breakthrough innovation ability has not been proved, and there is a significant positive correlation between tacit knowledge acquisition and cognitive tacit knowledge acquisition; (3) internal social capital and external social capital have a positive adjustment between open innovation and breakthrough innovation capability, and the former is greater than the latter.