Abstract: With the development and popularity of the Internet,more and more legacy applications based on the traditional software architecture want upgrading and restructuring to the web based Internet/Intranet architecture. Taking CTSS(Computer Tomography Scan System) for example, this paper introduces the system architecture,work principle and key technique of the web based system reconstruction solution scheme, which is based on the three-tier Internet/Intranet architecture,and at the same time, elaborates the use of JSP. XML in the system reconstruction.