Abstract: Based on the APCO theoretical model of privacy concerns and integrating the theory of privacy calculations, the research examines the impact mechanism of social media users’ privacy policy (including the understanding of privacy policy and the perception of effectiveness) on self-disclosure.We collected 579 effective questionnaires from social media users,and SPSS was used to analyze data.The research finds that social media trust has a mediating effect between privacy policy perception and self-disclosure. Privacy computing cost plays a moderating role between privacy policy perception and social media trust. When users' perception of privacy computing cost is low, privacy policy perception will promote self-disclosure through social media trust. This study finds that the influence path of privacy policy and self-disclosure is not a simple linear model, but a complex, multi-linear mediated effect model for the first time. The research results have a certain explanatory role in understanding the influence mechanism of privacy policy on self-disclosure and can further enrich the APCO.

Key words: Privacy policy, Self-disclosure, Social media trust, Privacy computing cost, Moderated intermediary effect；APCO model