Abstract:With the rise of the online learning boom and the popularization of the concept of lifelong learning, various social media platforms have become an important carrier for users to carry out learning and acquire knowledge. Therefore, exploring the connotation of users' perceived usefulness of online learning platforms and its antecedents helps platforms further tap their own value and provide users with better services. Based on this, using social learning theory as the foundation, semi-structured interviews were conducted to obtain raw data; subsequently, the qualitative research method of grounded theory was employed, and the qualitative analysis software NVivo was used to conduct systematic hierarchical coding, further clarifying the reasons why users find online platforms useful and the specific dimensions of usefulness, and constructing a corresponding theoretical model framework. At the same time, 26 interviewees were used as the research sample to understand their usage experiences and behaviors on social media and online learning platforms, so as to provide guidance for the future development of the platforms. Through coding analysis, it was found that the antecedents of users' perceived usefulness are content characteristics, user characteristics, and platform characteristics, which correspond to perceived informational usefulness, social usefulness, and technical usefulness, respectively. Therefore, these three types of usefulness constitute the multidimensional structure of perceived usefulness of online learning platforms. Specifically, the higher the content quality of online platform videos and the greater their value to users, the more resources users gain from social interactions on the platform, and the stronger the platform's system quality, the more users will perceive informational usefulness, social usefulness, and technical usefulness, respectively.