Background: The convenience and accessibility of social media has made it a promising channel for sexuality education worldwide. In China, the popularity of social media such as Bilibili among young users and the increase in sexuality education content on such platforms have sparked concerns over video quality and educational content. Few existing studies have focused on such issues. Objectives: This study aimed to evaluate the characteristics and quality of sexuality education videos on Bilibili, a popular video-sharing social media platform among young people in China, and to explore how video characteristics and quality affected audience engagement. Method: We conducted a content analysis of 203 sexuality education videos on Bilibili. Results and Conclusion: Reproductive health and sexual pleasure were frequently addressed topics, and non-professional individuals were the most common sources of information about these. The involvement of well-known social influencers directly affected user engagement. In addition, video quality had a significant positive impact on user response. The quality of the sexuality education videos was generally high, and of strong educational significance. Hence there may be value in seeing sexuality education videos on such media as supplements to school-based education. Practical implications for improving the quality of sexuality education videos on Bilibili and other social media platforms as well as theoretical insights are discussed.