The instrument landing system provides an important guarantee for the safe landing of aircraft. In view of the increasing number of flights, how to ensure the efficient and safe operation of ILS has become an important issue for the civil aviation department. Through theoretical analysis and research on modulation depth difference (DDM), it is concluded that the main factor affecting DDM is modulation factor m90 . On this basis, the mathematical models of channel and modulation factor and carrier negative value are established by using control variable method and least square method respectively. Based on NM7000 equipment, a simulation system was built to dynamically simulate the channel adjustment process. Finally, the accuracy of the model was verified by comparing the established system with the actual situation. The data showed that the relative error of simulation was less than 1%, indicating that the proposed model was of high accuracy and could provide theoretical support for the reference of air traffic controllers.