The article conducted an evidence-based analysis on the accessibility and utilization of medical service and the medical expenses of Nanjing residents. It pointed out that the accessibility of medical service was very good in Nanjing, unreasonable patients flow was the main cause of overly expensive medical service. Authors recommended to guiding the residents to make use of medical service reasonably, establishing whole population coverage social security system and raising the government input, in order to insure the essential medical service for Nanjing residents.