Abstract: Based on the theory of social presence, this article explores the cross-platform information communication effects and influencing factors of government new media using 2 031 pieces of data from the Sina Weibo, WeChat, and TikTok accounts of the S Provincial Traffic Police. Regression analysis is employed for examination. The results reveal that, from the perspective of social presence theory, government new media create public participation scenarios through content production, engaging the public’s attention to government information and helping them to accept and share it. Throughout this process, affective, interactive, and cohesive strategies supporting the construction of social presence generate differentiated communication effects on different platforms. Additionally, diverse content themes on different platforms also exert varying impacts on the information communication effects of government new media. Based on the above conclusions, government new media should be operated according to the characteristics of different platforms and actively create a sense of social presence to improve their communication effects. In terms of overall content positioning, relationship-oriented and other-centered information release strategies should be adopted. In terms of theme setting and strategy selection, operations should be differentiated based on the various dimensions of social presence, the technical logic of different platforms, and the active demands of users.