Aiming at the problem of partner selection in the process of virtual enterprise's establishment, this paper combines the rough number theory with extension evaluation to establish the rough extension evaluation method of partner selection, which is driven by the cooperation demand. Firstly, quality function deployment(QFD) is used to analyze the enterprise's cooperation demands and their importance degrees, which are translated into decision attributes and their importance degrees. In the deployment processing, the rough number is employed to deal with uncertainty semantic information, and the maximum entropy criterion is provided to the process of rough QFD. Then, based on the cooperation demands of enterprises, this paper proposes a rough extension evaluation method, which is used to recommend the most suitable candidate enterprises. Finally, the feasibility and effectiveness of proposed method are verified by case analysis and comparison.