In order to offer the quality of the people having thorough and persistent medical care services and to establish the medical idea of regarding patient as the centre as well as avoid the waste of resources of medical care, the demand of information exchange and data sharing between healthcare institutions is increasing day by day. In addition to the exchange the text-based medical information, the exchange of medical images becomes increasingly important as well. For the purpose of effectively fostering this exchange and sharing, it is necessary to rely on building a standardized and feasible information exchange model to support. Furthermore, owing to the most of medical information systems in the course of their implementations are not considered the issues of integration and scalability, therefore this paper presents an architectural model with a prototyping system implementation of agent-based common service gateway for the integration and exchange of medical information. The system architectural model is established by adopting the standards of HL7 and XML with integrating the healthcare standards of CDA and DICOM, and employing the technology of software agents to implement. It is anticipated to leverage this model to enhance the effectiveness and efficiency of medical information exchange and sharing. Moreover, to expeditely reach the goals set by our national medical authority to promote and strengthen (1) the optimization of the utilization of medical resources, (2) hierarchical medical treatment system, (3) strengthen the integrity of referral message, and (4) the integration of information systems. The proposal of this architectural model hopefully can provide a reference model for nationwide medical institutions and health care institutions to build similar systems and as a basis for industrial professionals and academic researchers to conduct further research so that the vision of nationwide medical information exchange and sharing can be accelerated to achieve.