Social networks have become an indispensable activity in people's lives. A number of previous studies have investigated various social networks and probed in the core knowledge of integrated social networks. While social network knowledge is general and extensive, few studies have delved into the core knowledge of individual social networks, especially Facebook, which is a social network with over 1.7 billion users worldwide. Therefore, this study aimed to elaborate on the core knowledge of Facebook. In this study, a total of 4429 relevant academic papers were collected from the Web of Science, an online electronic database. Then, citation analysis and co-citation analysis were adopted to identify 50 highly cited academic papers to form a co-citation matrix. Finally, cluster analysis and multidimensional scaling analysis were employed to determine the core knowledge of Facebook. The research results showed that there are six points of core knowledge: (1) the behavior analysis of users; (2) the social impact of social networks; (3) the influence and application of Facebook in universities; (4) the evaluation of use motivation and theoretical models; (5) privacy risk and interpersonal impression; and (6) the strategies of social networks. The research results could be useful for academic studies and practice in the future.