Open innovation has become one of the important ways of obtaining external knowledge resources and enhancing innovation capability of enterprises. In the field of innovation performance, the literature of comprehensive consideration of internal R&D investment and external Knowledge acquisition are relatively few. Based on literature review and commentary, this paper examines the in?uence of R&D con?guration on innovative performance and the moderating role of a ?rm’s R&D capacity in China's manufacturing industry with reference of the Tobit estimation model. It’s data is from S&T statistics data and 2,905 sample enterprises. The ?ndings suggest that ?rms that increasingly rely on external R&D activities have a better innovative performance, yet up to a point. Beyond this threshold, a greater share of external R&D activities reduces a ?rm’s innovative performance. And such substitution effect is larger for ?rms with greater R&D capacity. This paper provides a better understanding opportunity cost for further opening up R&D borders is higher for ?rms with a superior technological knowledge stock.