Taking Bilibili danmaku video sharing website as an example,this paper selects 33 popular danmaku videos in December 2017 as research sample, and employs the content analysis method to investigate the motivations and behaviors of Bilibili users. The results show that the motivations of digital youth consist of information needs, entertainment needs, and social enhancement needs. Furthermore, there are 14 sub-behaviors derived from these needs. The research findings may yield some practical implications for the information architecture,user experience design,and sub-cultural managerial issues of danmaku video sharing websites.