A method of requirements validation is developed and defined to meet the needs of civil aircraft requirements validation in product development. Based on requirements project principle, this method will not affect the conventional design elements, and can effectively connect the requirements with design. It realizes the modern civil aircraft development concept, which is “requirement is the origin, design is the basis”. So far, the method has been successfully applied in civil aircraft aircraft development in China. Taking takeoff field length as an example, the validation process and the validation method of the requirements are detailed introduced in the study, with the hope of providing the experiences to other civil aircraft product design.