Although QFD is powerful for translating customer requirements to control parameters of product design and production process, how to capture and understand requirements rapidly, accurately and economically so that the products can deliver themselves of customers is still a bottle-neck. This paper proposes a theory framework for capturing customer requirements. First, the problem for customer requirements capture is formalized. Second, three phases including requirements gathering, requirements mapping and requirements evaluating are advanced, and a method named iterative arithmetic to determine the weights of requirements is also developed. Finally, the proposed methodology is effectively demonstrated in an instance of requirements capture for reading lamp of computer.