R&D internationalization is an important way for enterprises in emerging economies to achieve technology catch-up and maintain sustainable development. The direct relationship between R&D internationalization and innovation performance has been widely explored, but the research on the influence of the mechanism between these two elements above is relatively less. This paper takes China’s knowledge-intensive listed enterprises from 2009 to 2015 as the research object and uses Poisson fixed effect regression, hierarchical regression, and bootstrap methods to study the mechanism of knowledge base between enterprise R&D internationalization and innovation performance and the moderating effects of institutional distance on the mechanism effect. The results show that: (1) Enterprises’ innovation performance can be promoted with the increase of R&D internationalization degree and diversity. (2) Knowledge Base (scope and entropy) plays a mechanism function between R&D internationalization and innovation performance. (3) By negatively moderating the relationship between the knowledge base and innovation performance, the institutional distance between home and host country negatively moderates the knowledge base’s mechanism function.