The relationship between knowledge-flow and task of collaborative design was analyzed. In order to control knowledge-flow in collaborative design, a resource space model was used to depict knowledge and a method to depict knowledge through matrix was presented in the resource space model, which could control and manage the contents of knowledge-flow conveniently. Collaborative design was driven by workflow. Through integration between knowledge-flow and workflow, an integrated control panel was presented and two integrated control algorithms for knowledge-flow and workflow were given. Finally, a prototype system was developed to assist to control knowledge-flow in collaborative design and the control of knowledge-flow in collaborative was realized.