Abstract: This paper selects five top-ranked public security government Tik Tok accounts, such as "SHEN Zhen Traffic Police" "WEN Zhou Traffic Police" "CHAN Cheng Public Security" "SHAN Xi Traffic Police" "TIAN Jin Traffic Police", and focuses on the interaction between the government and the people in the comment area to discuss the discourse practice of public security government Tik Tok, using participatory observation combined with text analysis and discourse analysis. This study finds that the themes of public comments are diverse and friendly, and there are more about "communication" than "government affairs". From the perspective of government, the use of expressions, online language and other elements in its interaction shows the "de-identification" shift. In addition, the focus of public attention in the comments is shifted from the theme of the short video. The government mostly plays the role of responder in the comment, and the awareness of actively setting up issues and the responses to questioned comments are relatively lacking. The paper recommends that public security government Tik Tok should take the multi-sensory advantage of short videos to serve the transmission of information, strengthen the response to questioned comments, and actively set the agenda for comments to build a whole interactive chain.