The Manufacturing Grid domain is characterized by rapid and substantial change over time. The entire process of product development can be quite complex. The activities are expected to be executed on heterogeneous resources which are geographically distributed. However, traditional modeling systems use static workflow models which can not automatically redesign the business process and mask the isomerism of the resources. In this article, an open and extensible framework of MG workflow is given, which complies with the standard of WFMC and GGF. A formalized definition workflow model is proposed including process model, organization model, resource model, and service mode. The integrated workflow model can be used to dynamically represent a business process and other aspect s of Manufacturing Grid workflow.