This study focused on the case of a knowledge team in Harbin Institute of Technology. Using social network analysis, the team’s knowledge sharing network was built and the network’s quantitative measurements were conducted. The contextual factors that hidden behind the data were collected through structured and semi-structured interviews based on the quantitative results. Then, from the semiformal organization and situated learning perspective, some contextual features of this knowledge-sharing network were revealed including the “identity” and “power” of “central” members, the “participation” of “peripheral” members and the formation of “knowledge-sharing groups”. On this basis, a conceptual model of semiformal organization’s knowledge sharing performance was developed from three angles, including individual situation, organizational context and organizational support.