A new method is presented to compensate the quadratic phase aberration introduced by Micro-Objective (MO) in Pre-magnified off-axis Digital Micro-Holography(DMH). It can realize the numerical compensation for the quadratic phase aberration on the back focal plane of the MO. By using this method, one parameter only need to be adjusted numerically to compensate the phase aberration and also only one hologram is needed.And, the auto-calculation for the reconstruction distance is performed in term of the spectrum information characteristic of back focal plane of MO.The experimental example is presented with a phase grating used as a testing specimen. The experimental results validate the presented numerical compensation method right and validity. Some experimental conclusion and analysis are also given at last.