Abstract: Effective scientific communication is essential to social governance of public health emergencies. The traditional model of science communication is “deficit model,” which aims at filling up the deficit among the public in scientific knowledge. This model cuts off the production and dissemination of scientific knowledge, requires high accuracy and low timeliness of the communicated knowledge, and includes little of the dialogues between the scientists and the public. The faultiness of the model have been exposed in the governance of COVID-19 outbreak in China: The scientists’ overwhelming emphasis on knowledge production and relative ignorance of scientific communication damaged the knowledge supply for the government and the public in decision. In limited scientific communication to the public, the estrangement between scientific expression and ordinary language brought about popular misunderstandings of risks in the epidemic. Therefore, the building of social governance system needs the transition of scientific communication from the deficit model to the dialogue model or the co-production model, integrating the production and communication process of scientific knowledge, and fully considering the difference of social and scientific contexts during communication, so as to achieve the timely and effective scientific communication.