Abstract: The existing access control models are imperfect to meet the requirements for a collaborative design system nowadays. Based on the characteristics of collaborative design and RBAC (role-based access control) model, a new model named MDACM (message-driven access control model) is developed to solve security problem due to the distributivity and dynamic ability of collaboration through an authority that is expressed by a message entity or integrated message entity in combination with filter rule, then control by static allocation. Moreover, the workflow control base is introduced into the model to affect message entity and support the workflow management of computer-supported collaborative design system. An application as example is given to demonstrate the effectiveness of the model.