Product agile customization design is an effective technological measure to win the customers and improve development efficiency. It needs designer to determine product structure quickly according to customer’s customized requirements. In this paper, a novel design method of product agile customization is presented by integrating rough set (RS) theory and artificial neural network (ANN) in the design process. In the method, design demands are reduced so as to form effective decision conditions by applying RS, and on that basis ANN models between design demands of different design stages and corresponding product structures are established so as to determine product structural styles quickly by applying ANN. Finally, this method is applied to the general schematic design process of a roll plate machine’s customization, and its validity is verified.