[Purpose/Significance] To explore the characteristics and inherent rules of health information interaction behavior among young social media users, and provide measures and solutions for social media intervention in users' positive health behavior. [Method/Process] In this paper, by collecting interview data, log files, experimental video data and Xiaohongshu note data, and adopting the data analysis methods of grounded theory and text mining, an in-depth analysis was conducted on the characteristics of young social media users' health information acquisition behaviors, the logic of health information quality evaluation, and the patterns of health information retrieval behaviors. And based on Engeström's Activity Theory and Kuhlthau's Information Search Process Model, an activity model of the health information retrieval behavior patterns of young social media users was constructed. [Result/Conclusion] The following conclusions were drawn: The sources from which young social media users obtain health information exhibit the characteristics of diversified choices that are mainstream-oriented and demand-driven. The ways in which they pay attention to health information content are mostly demand-based retrievals triggered by recommendations, and the categories of attention fall into multiple core areas of concern. Young social media users' evaluation paths for health information quality follow a dual path of subjective cognition and objective perception. The basis for judging the trustworthiness of health information is a collaborative inspection-style information assessment through the convergence of content and the consensus of comments, and the evaluation method of health information is based on the principle of the minority obeying the majority.