This study investigates what roles the Chinese state-owned media play in the Covid-19 outbreak in terms of what kind of messages they delivered on Weibo and the quality of the messages. It also explores how the public is engaged with these messages on Weibo. Both the messages and the engagement are examined by mix-method content analysis.   The exploration of the Weibo messages relies on the Crisis and Emergency Risk Communication (CERC) framework. The CERC framework combines various existing theories and compiles them into a communication guideline for a health crisis. This study examines the messages by focusing on sensemaking and self-efficacy. Sensemaking is informing the public of the nature of the crisis; self-efficacy reflects people’s confidence in the capacity to change behaviours and deal with the problems. It was found that Weibo provides a platform for delivering sensemaking messages and self-efficacy messages in the coronavirus outbreak. However, considering the accuracy, relevance and intelligibility of strategic health communication, the quality of the messages is debatable in some cases.   The exploration of social media engagement relies on Liu, Lu and Wang’s virality theory on social media which discusses four aspects of engagement: authority, privacy, evidence and incentive appeal. This study shows how each of these aspects influences how people engage with messages on Weibo: the effect of different authorities on the message engagement; the usage of one-to-one communication and one-to-many communication in the engagement; and the engagement in positive appeals and negative appeals.