This paper presents an application framework for constructing sketch-based cooperative design (especially for distributed conceptual design) tools. Three key issues are addressed: (1) how to represent and store sketch document; (2) how does the system infer the designers' intention and help them to complete the design process; (3) how to implement the communication between the client and the server. Solutions to these problems are proposed in this paper. The framework has been implemented and tested on a variety of applications, for example, cooperative UML diagram design. The primary experiments demonstrate the efficiency of the proposed framework.