Based on many theoretical explorations and practical discussions，this report re-examines the mainstream media’s “short video” dissemination practices and their discourse characteristics from three levels of communication，mobilization，and supervision during the COVID-19 pandemic. This report holds the following statement to be true：firstly，in the era of platform-based communication，short video of mainstream media has three technical and cultural characteristics：mobile priority，dual screen complementary，production with networking style and convergence reversely. Secondly，at the practical level，the mainstream media short videos on “anti-epidemic” present a feature of multimodal discourse，an intermediary narrative strategy，and timely mobilization and social supervision effect. This report puts forward that in major public events，the production and dissemination of mainstream media short videos need to create a people-centered content ecology，form an interactive pattern of “media curation and public participation”，and establish a cross-platform collaborative communication mechanism，which can effectively promote the level of social information governance.