Tn the modern integrated healthcare environment, digital technology plays a critical role in the success of its operation. For overcoming the deteriorated healthcare management environment is to improve business service ability, cost and management efficiency through information processing of the business service process and the decision support system. For a solution of these problems, the Hospital Information System(HIS) was introduced. In this paper we proposed HIS system through the HL7-based with legacy system that improves both the efficiencies of medical of office and medical treatments. The implementation of HIS system enables combination of legacy systems including HL7 based OCS and PACS. And we proved the effective HIS development method provided by analysis of total module.