Since OPC DA Server is base upon the technology of COM/DCOM, its technical defect has appeared prominently while exchange the data with each other between the Internet. Thus it's important to lead out the technical advantage and the necessity of OPC XML-DA Server based on the Web Service technology. The exchange of plant data across networks has been facilitated, in the meanwhile, the Data Fusion between Management Information System and FCS has been promoted. This paper presents the scheme of a Middleware Server which is realized by mean of gSOAP Development Kit. The interface of the DA Server based on the technology of COM could be connected with Web Service Interface based on the technology of XML/SOAP. The experiment executed on two computers deployed in different networks justifies high efficiency and feasibility of OPC XML-DA Server in the communication.