Abstract: Existed theories related to the inherent mechanism as to how knowledge transforms into radical innovation are still unclear, which may lead a firm to be puzzled by how to gain competitive advantage via external knowledge. The study, with the 208 High-tech enterprises in China as an object of investigation, discusses the relationship between knowledge attribute (tacit knowledge and complexity knowledge) and enterprise radical innovation, and analyses with contingency approach the moderating effects that enterprise social capital makes in knowledge attribute and radical innovation. The results show that, complexity knowledge has direct effects on radical innovation. In addition, with the structural dimension enhances, enterprises will absorb more outside tacit knowledge to turn into radical innovations and with the cognitive dimension enhances, enterprises will absorb more outside complexity knowledge to turn into radical innovations. Finally, the present paper discusses managerial implication and future research.