In the course of network supported collaborative design, the data processing plays a very vital role. Much effort has been spent in this area, and many kinds of approaches have been proposed. Based on the correlative materials, this paper presents extensible markup language(XML)based strategy for several important problems of data processing in network supported collaborative design, such as the representation of standard for the exchange of product model data(STEP)with XML in the product information expression and the management of XML documents using relational database. The paper gives a detailed exposition on how to clarify the mapping between XML structure and the relationship database structure and how XML-QL queries can be translated into structured query language(SQL) queries. Finally, the structure of data processing system based on XML is presented.