Abstract: Fu 3 member in Qutang sub sag of Hai'an sag has characteristics of deep buried depth, small sandstone thickness(1.3～3.0 m), the lithology is mainly of argillaceous siltstone and silty mudstone, and the wave impedance is overlapped. As conventional wave impedance inversion cannot meet the demand of actual production, the impedance curve of natural gamma wave was reconstructed to predict the trend of sandstone plane. By using the relationship between sand-ground ratio and wave impedance distribution,the effective sandstone reservoir data body was described, and the spatial distribution regularity of hidden oil and gas reservoirs in Fu 3 member of Qutang sub sag was described. The results showed that the inversion results of wave impedance reconstruction in this area were in good agreement with the well seismic data and the reservoir prediction error was small, which provided an effective technique for reservoir prediction of lithologic reservoirs and structural-lithologic reservoirs.