Abstract: Government short videos have become an important tool for government affairs disclosure, government-citizen interaction, public opinion guidance and social governance. This paper takes 792 government short videos released by “Healthy China”, an official TikTok account of the National Health Commission of China, from December 27, 2019 to January 8, 2023 as the research object, and the heuristic-systematic model of information processing as the theoretical basis, to comparatively examine how the content type and video length as systematic clues, and the dialogue loop, crisis communication strategies and title length as heuristic clues affect citizen engagement behavior in crisis and post-crisis situations. The results show that compared with service appreciation information, the latest news about the COVID-19 crisis, the governments’ responses and stakeholders’ guidance can all have positive impacts on passive engagement in crisis situations. However, all of them have no effects on passive and active engagement in post-crisis situations. In terms of crisis communication strategies, compared with information strategy, support strategy can promote passive engagement, while adaptation strategy has no significant effect on both active and passive engagement in crisis situations; in post-crisis situations, support strategy positively affects passive engagement, while adaptation strategy positively influences active engagement. The effects of dialogue loop on both active and passive engagement are not significant in crisis and post-crisis situations. In crisis situations, the title length positively affects both passive and active engagement, while in post-crisis situations, the title length has a positive effect on active engagement but a negative effect on passive engagement. In crisis situations, video length reduces passive engagement, but promotes active engagement, while in post-crisis situations, it promotes passive engagement.