Ruyi Dan, a medicine reputedly effective against epidemics and many other disorders, has been mentioned in writings connected with the Jingming movements as early as the Southern Song dynasty. It is also mentioned in the pharmacognostic writings of the Ming and Qing dynasties. Although some claims connect it with Xu Xun and Ding Yi, it could not have been created before 1128. This paper relates it to the development of the Jingming movements and to the serious epidemics during the early Southern Song. The later Jingming movements of the Yuan and Ming dynasties recruited members by promoting its curative powers.