This paper presents an aircraft modeling method based on flight dynamics. The real-time geographic coordinates, flight altitude, attitude, heading and speed of aircraft are considered, and the control variables of aircraft rudder surface and pilot response model are introduced. The motion attitude of the aircraft was decoupled into vertical direction and horizontal direction, and a 6-DOF dynamics model was built based on the performance constraints of the aircraft itself. The number of flight parameters is given by simulation and the descent rate at different altitudes is obtained. The feasibility of this method is proved by the comparison with the Honeywell official alarm envelope obtained by linear fitting, so as to judge whether there is potential danger for the aircraft.