In public health emergencies， how to quickly establish trust and transfer authoritative and professional medical information through appropriate channels and methods in society is the key to emergency response. By analyzing the public opinion index of new online media， this study explored the peak and trend characteristics of social communication conducted by medical experts in the outbreak of COVID?19， and analyzed the effectiveness and characteristics of information transmission. The medical information voiced by authoritative experts has aroused a high social concern， showing a rapid growth and high trends. The high peak of hot spots is closely related to the critical nodes of the epidemic. Effective medical information transmission under the outbreak needs to reflect authority and professionalism in all aspects of social communication，and the social communication strategy in emergency prevention and control of major epidemic situations can be further optimized with the public data support.