The paper introduces the concept of the third space, and discusses the advantages of medical university libraries in opening the third space for social services by use of their own environment, resources and talents. It elaborates on the social significance of providing the third space by medical university libraries for external services from the aspect that it can meet the requirements for medical knowledge and new-type recreation and entertainment of medical and social people in a larger area, enhance social harmony, and the self-value demand and a new healthy lifestyle.