The description of product concept space and the evaluation of product projects are important for product conceptual design. In this paper, the structure and character of BOM were analyzed, and the description of product concept space based on BOM was proposed. A model, including the attribute solving of function and carrier fields, was established to get the best designing scheme. AHP was introduced to solve this model, and the results were validated by a case. The results show that the alternative design proposal can guarantee product function request and has good technical performances, such as optimizing the description of product concept space, improving the design efficiency.