Abstract: In this paper，we discuss the characteristics of collaborative design over Internet and the corresponding requirements to workflow management system （WfMS）．We also propose the software architecture of a web-based WfMS named co-Flow ，and introduce the XML-based workflow process definition along with the mechanism that facilitates interoperability of distributed workflow engines in detail．Prototype of such a WfMS has been developed in our laboratory and it is fit to be used for inter-enterprise collaborative design．