In order to fastly and accurately reconstruct the three-dimensional information of the hologram recorded by pre-magnification digital micro-holography, the solution of phase compensation in pre-magnification digital micro-holography with equal-cruvature object beam and reference beam is studied theoretically and experimentally. The point spread function is derived, then the expression of reconstructed light field amplitude and phase aberration are obtained, and by using phase mask to pre-compensate with the phase aberration fastly, the phase for the reconstructed light field is unwrapped. At last, combined with automatic phase compensation, the accurate phase distribution of the sample is obtrained. The red blood cells are researched experimentally. The result shows that phase mask to pre-compensate, not only can avoid the error in phase unwrapped, but also effectively eliminate the secondary phase distortion in the reproduction of light field, which aims to achieve the right phase distribution using single automatic phase compensation method.