To investigate the effect of flap deflection on aerodynamic performance of the parafoil, CFD models are established for different flap deflections. By using the finite volume method, the spatial discretization is carried out and the RANS equation is solved. The aerodynamic performance of the parafoil in the stage of turning and flaring is simulated, and then combining with the least square procedure, parameter identification is carried out to implement the modification of the parafoil aerodynamic model. Simulation results show that the flap deflection can cause the change of the parafoil pressure distribution, the decrease of the stall angle of attack, the sudden increase of the lift drag coefficient, and the complex effect on aerodynamic performance of the parafoil. Compared with the traditional aerodynamic model, the modified parafoil aerodynamic model can better describe the regulation of the flap deflection and the aerodynamic performance of the parafoil, and the calculation precision is improved effectively. It provides a theoretical reference for precise modeling of the parafoil in the stage of turning and flaring.