Based on the actual application of Moiré fringes for the alignment of lithography, the modulating regulation on Moiré fringes produced by generic and line gratings is discussed according to Fourier optics in this paper，and the low frequency(1, -1) class Moiré fringe which is extensively applied was simulated. Aimed at two grating marks of the little difference from repeated frequency for the alignment of lithography, the magnified Moiré fringes would be produced with the characteristic sensitive to displacement，which was explained by simulation. Thus，high alignment accuracy of lithography was achieved. Finally, the alignment accuracy of lithography by the alignment method was analyzed briefly.