Abstract: The target zones of the Mesozoic in X block in North Yellow Sea basin are characterized by deep, tight and vertically-horizontally varied reservoirs. According to the statistical analysis of logging data, the velocities of sandstone and mudstone in the target zones are similar, and the distribution range of P?wave impedance is overlapped. This paper proposed a set of approaches for dealing with the problem of prediction of reservoir porosity in sandstone and mudstone with overlapped wave impedance: 1)using sensitive lithology curve to reconstruct interval transit time curve and then take inversion;2)distinguishing the sandstone and mudstone by reconstruction and inversion of interval transit time curve, obtaining the original wave impedance value of the sandstone by using sandstone matrix constraining and inversion data;3)based on the relationship between the original wave impedance and porosity, convert the sandstone wave impedance into porosity. The case study shows good results in application of this method to this area