A self-consistent Green's Function approach is used to study the in°uence of short   range correlations beyond the mean field approach of nuclear matter. The ladder equation, including both particle-particle and hole-hole propagation, is solved in nuclear matter for a realistic interaction derived from the CD-Bonn potential. The hole- hole interaction is used to calculate the spectral functions that describe the distribution of holes below Fermi level. The nucleon spectral functions are calculated from the momentum and energy dependent self-energy. For comparison, the calculations are investigated by including nuclear three-body force. These spectral functions directly re°ect the e®ects of the nucleon-nucleon correlations and can be explored by the analysis of nucleon knock-out experiments like (e, e'p).