[Purpose/significance] Generation Z (Gen Z) users account for more than half of China’s social media us⁃ ers. Their social media culture characteristics including (1) meme as a language，(2)leveraging the technology to cope with the negative influences that social media platforms posed，(3)Finsta culture. Understanding Gen Z users’informa⁃ tion posting behaviors in social media, can provide empirical references for understanding their preferences on their us⁃ age and intentions of Internet activities. [Method/process] Through theoretical sampling, semi-structured interviews were conducted among 12 Gen Z users who had both primary and secondary accounts on the same social media plat⁃ form. Based on grounded theory, the transcript of the interviews was analyzed. Finally, 6 core categories are identified, namely, Gen Zs’use purpose on social media, privacy cognition, interpersonal relationships cognition, information re⁃ ceiver cognition, spaces’boundaries setting on social media, and social media information posting behaviors. The rela⁃ tionships among the 18 specific categories and the 3 transformation paths of users’migration were discussed. [Result/ conclusion] Gen Z users“social disconnections”“emotionexpressionandself- emotion regulation”,and“self- develop⁃ ment”usage needs on social media promote their resetting on spaces within same social media platform. Such informa⁃ tion practice creates and enhances Gen Z users’new cognition on online interpersonal interaction that is“Secondary Account as Privacy”. Based on such cognition, Gen Z users can redefine the boundaries of“privacy space”on social media, by controlling the posted information’s scope, content’s context, and frequencies. Based on that, this paper dis⁃ cusses the user experience optimization service approaches, from the perspective of the platform and users.