Educational data mining has become an important research field in studying the social behavior of college students using massive data. However, traditional campus friendship network and their community detection algorithms, which lack time characteristics, have their limitations. This paper proposes a new approach to address these limitations by reconstructing the campus friendship network into weighted directed networks in continuous time, improving the effectiveness of traditional campus friendship network and the accuracy of community detection results. To achieve this, a new weighted directed community detection algorithm for campus friendship network in continuous time is proposed, and it is used to study the community detection of a university student. The results show that the weighted directed friendship network reconstructed in this paper can reveal the real friend relationships better than the initial undirected unauthorized friendship network. Furthermore, the community detection algorithm proposed in this paper obtains better community detection effects. After community detection, students in the same community exhibit similarities in consumption level, eating habits, and behavior regularity. This paper enriches the theoretical research of complex friendship network considering the characteristics of time, and also provides objective scientific guidance for the management of college students.