Abstract: EXPRESS language should be transformed into XML language when applying STEP-NC, a new NC programming language, to the cooperative manufacturing within a network for the integration and share of the product information among manufacturers, thus enabling them to share and exchange the information under remote and heterogeneous conditions. The data types and features of EXPRESS and XML languages and the mapping method between them are discussed, then two transformation techniques between them are put forward on the basis of XML schema library and DOM interface. The way of how to use DOM interfaces to implement the transformation definitely is therefore given to support technically different manufacturers to develop their cooperative product designs for networked manufacturing.