Collins formula, which describes the diffraction of light wave passed through a near-axis optical system, and its inverse calculation expression are presented in this paper. The object plane and charge coupled device (CCD) detector plane which are used in the study of digital holographic detect, are treated as the input and output planes of an ABCD system. An algorithm of wavefront reconstruction is put forward based on the anti-calculation expression of Collins formula. In order to be applied easily in practice, the frequency spectral structure of a hologram when the reference light is a spherical wavefront, is researched. It is demonstrated in theory that the frequency spectra of object wave and its conjugate wave, which can be separated through a wave filter, exist in the frequency space of a hologram. Thus, via the theoretical simulation and experimental result the possibility of wavefront reconstruction using the anti-calculation of Collins formula is proved.