Abstract: Besides the aberration, the overlapping with 0th and ±1st images observed in the phase distribution is difficult to deal with, which is different from the phase compensation methods adopted in off-axis setup. A method was proposed to get the phase information from a single in-line Fresnel digital holography. By subtracting recoded hologram by a numerical hologram, effect of the phase curve, the 0th image and the diffraction of the rectangular aperture was eliminated. The phase can be retrieved. The theoretical analysis and the experimental results were presented. It is found that better phase result can be obtained than former digital phase mask method.