A local grid deformation method based on TFI(Transfinite Interpolation) was developed in this paper. This method could be employed to solve complex flow with other dynamic grid methods because it is different from other global grid deformation methods while it can limit the deformation in special zone without any influence on grids of other zone. For an airfoil NACA0012 with a flap, numerical simulations of pitching oscillations were conducted, and computational results agrees well with experimental results. Then it is concluded that the method developed in this paper is variable for flow solutions of complex geometries.