ABSTRACTInnovation is a process of knowledge recombination [Fleming, L. 2001. “Recombinant Uncertainty in Technological Search.” Management Science 47: 119 p]. Extant literature highlights the importance of a firm’s knowledge base for innovation, while little is known about the structure of a firm’s knowledge base and how it affects the firm’s explorative innovation. Based upon the perspective of network analysis, we portray a firm’s knowledge base as an intra-organisational knowledge network and examine the effects of two structural features of the network – density and centralisation – on the firms’ exploratory innovation. Using a manual collected dataset of 738 Chinese automobile manufacturers, we find that a firm explores fewer new knowledge elements when the firm holds a dense knowledge network or a centralised knowledge network. More importantly, with the increase of a firm’s R&D collaborations with external actors, the negative effect of density is mitigated while the negative effect of centralisation is reinforced. Both theoretical and practical implications are discussed.