This study contributes new insights into digital multimodal composing (DMC) using a multimodal analysis of two COVID-19-related videos embedded in a virtual ethnography of social media platforms in China. The analysis examined how video-makers drew on meaning-making resources and multimodal techniques in DMC to enact practices of civic participation at a time of crisis. The findings revealed two new modes of civic participation enacted through DMC: popularizing scientific knowledge of safe living at a time of confusion and discriminations, and inspiring people to fight the virus and fears with courage and hope. The findings also show that these forms of civic participation were mediated by ingenious remixing practices and gave rise to participatory communities with local and global reaches. The study argues that DMC renders a new avenue for civic participation. Implications on how DMC can be used for civic purposes and digital citizenship education are discussed.