The invention discloses a method for identifying a fixed-order parameter model of an aircraft based on modal segmentation and genetic algorithm, which belongs to the field of aircraft identification modeling. The invention is characterized in that the method comprises four stages, namely, model structure determination, flight data acquisition, model identification and model validation, wherein the stage of model structure determination is used for establishing a modal segmentation model of the aircraft, and comprises three steps, namely, kinetic analysis, model order determination and modal segmentation model determination; the stage of flight data acquisition is used for obtaining the frequency-domain response data of the aircraft, and comprises three steps, namely, sweep-frequency flight experiment, frequency domain transformation and data response of frequency domain; the stage of model identification is used for identifying the obtained dynamic model of the aircraft, and comprises a step of identifying model by using the genetic algorithm; and the stage of model validation is used for verifying the obtained dynamic model, and comprises a step of model validation, wherein, in the stage of model structure determination, the complicated high-order dynamic models are simplified by using the modal segmentation model, so that the precision of the model is not restricted by the model order in the process of identification while all unknown parameters are kept; in the stage of flight data acquisition, the true dynamic frequency response of the aircraft is obtained; in the stage of model identification, the modal segmentation model is upon the true dynamic frequency response to the greatest extent by using the genetic algorithm; and in the stage of model validation, the obtained dynamic model is inspected, in case of meeting the requirements, all identification models meet the requirements, otherwise, an experiment is carried out again.