As a group learning model 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 establishes 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 illustrates that traditional classroom learning network and project-based learning network are mainly divided according to class borders, and the daily communication network has broken through the boundaries of administrative classes. The three types of networks have some similarities in structure, but the daily communication network has higher concentration and centrality. In traditional classroom learning network and project-based learning network, the membership overlap is more common, and most of the members are excellent students. Daily communication network has more small circles. 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 project-based learning, suggestions are put forward including encouraging students to increase communication in their daily study and life, allocating excellent students and active students in project-based learning, motivating more excellent students to join in, and appropriately allocating some opposite-sex members to the team.