<p>This paper presents a morphing missile with an expandable flared skirt, which aims to change aerodynamic shape according to the change of flight environment to improve flight efficiency. The morphing missile with an expandable flared skirt is regarded as a multi-rigid-body system, and the six-degree-of-freedom(6-DOF) nonlinear dynamic model of the missile is established considering the changes of aerodynamic force, mass distribution, and inertia characteristics during morphing. In order to investigate the longitudinal dynamic characteristics of the missile, the nonlinear dynamic model is de-coupled to obtain its longitudinal motion equation. The aerodynamic parameters of the missile in the whole flight state envelope are simulated by quasi-steady assumption, and the aerodynamic coefficients under different flight environments and flared opening angles are obtained. The aerodynamic coefficients obtained from the simulation at each operating point are fitted to the flight altitude, Mach number, and the morphing rate of the flared skirt by the least square method. Finally, the parametric model of the aerodynamic coefficients is obtained. Finally, the aerodynamic coefficient function model is introduced into the longitudinal motion equation of the missile, and the longitudinal dynamic characteristics of the missile in different flight conditions are obtained by numerical simulation. The simulation results show that the morph of the flared skirt has a significant influence on the longitudinal motion characteristics of the missile.</p>