As one of group learning models characterized by project-driven, "learning by doing", project-based learning has been widely applied in many universities. In order to explore the formation mechanism of project-based learning, this paper established three types of whole networks of daily communication, traditional classroom learning and project-based learning for college students from the perspective of students' communication. Social network analysis illustrated that the traditional classroom learning network and project-based learning network are mainly divided according to class borders, and the daily communication network has significant cross-class structure; The three types of networks have some similarities in structure, but the daily communication network has higher concentration and centrality. In the traditional classroom learning network and project-based learning network, the membership overlap is more common, and most of members are excellent students; Daily communication network has more “small circles”, which are characterized by some separated groups internally contain several tightly connected members. Most nodes in traditional classroom learning and project-based learning network are interactively connected. The regression results show that daily communication network and traditional classroom learning network have positive and significant impact on project-based learning. In order to promote the project-based learning, suggestions include encouraging students to increase communication in their daily study and life, allocating excellent students and active students in the project-based learning, motivating more excellent students to join in, and appropriately allocating some heterosexuals to the project-based team.