Abstract: The aerodynamic calculation of flap deflection is a key program of parafoil modeling. In order to improve the precision of parafoil dynamic model, an aerodynamic model of flap deflection was proposed based on a method combining CFD numerical simulation with least squares identification. Numerical simulation based on dynamic mesh was used to observe the change of parafoil shape and posture, which was responsible for obtaining aerodynamic data. Least squares used to identify the parameters of model, which was responsible for aerodynamic calculation of flap deflection. Research results show that, the aerodynamic model of flap deflection can better describe the aerodynamic rules of parafoil and the simulation results of parafoil dynamic model are close to airdrop test data, which verifies the effectiveness of the modeling method in this paper and provides a new idea for precise modeling of parafoil.