Abstract: Parametric programming was adopted on the modeling of deformable trailing edge flap (DTEF) to realize its flexible deformation and control, based on which numerical simulations were conducted to analyze the effects of DTEF on aerodynamic performance of the wind turbine airfoil and to study its flow mechanism respectively under static and dynamic conditions. Results show that under static conditions, the angle of flap affects the lift coefficient and drag coefficient obviously; with the rise of attack angle, the ability of DTEF reduces in changing the aerodynamic performance of the airfoil, and its influence on neighboring flow field weakens accordingly. Swing DTEF makes the change of lift coefficient of airfoil lags the change of flap angle, with reduced ability of DTEF on the control of lift coefficient; whereas swing DTEF makes the change of drag coefficient leads the change of flap angle, with enhanced ability of DTEF on the control of drag coefficient; these unsteady effects of flap oscillation are enhanced with the decrease of the oscillation cycle, reflecting in the variation of surface pressure coefficient of airfoil and in the development of wake vortex.