In this paper a modified dislocated grids scheme combined with the FFT-based method is proposed to reduce the burden of the near correction matrix.The scheme first adopts two sets of dislocated Cartesian grids that are respectively applied to projections of the field points and the source points.Then parts of Green's function values are modified for further improving the accuracy of fitting.When the proposed scheme is applied to the Real coefficients Fitting Green's function Fast Fourier Transformation

the number of near correction elements is reduced.Compared with the traditional uniform grid scheme

the new scheme has lower total memory requirement and higher calculation speed.