The pollution force of medical waste water is strong, the discharge of waste water will seriously pollute drinking water supply and spread diseases. In the higher standard of present medical wastewater emission index, it is inevitable for the hospital to transform the past simple sewage treatment facilities and technique. Taking the transformation of a comprehensive class 2hospital sewage treatment plant for an example, the engineering, process operation effects before and after treatment were compared, and the results show that engineering structure design should pay attention to near-term and long-term plan, the late increased grille greatly reduce the amount of suspension and floater in the septic tank, and solve the pipeline block problem; Hydrolytic acidification tank design is more accordance with the specifications, and can satisfy the requirement of removing ammonia nitrogen in hospital wastewater, the result can provide reference for similar hospital to transform the sewage treatment plant in the future.