Abstract: Exploration practice shows that the development of sandstone interlayers or carbonate interlayers in organic-rich shale intervals is one of the key factors for shale oil enrichment and high yield. At present, there is no quantitative evaluation model or method for the development degree of these interlayers. The quantitative evaluation model of relative hypertonic interlayers in shale is established. It is of great significance to improve the quantitative evaluation process. A mathematical model for characterizing the development of the interlayers is established by using the position and dispersion of interlayers in a formation. Based on seismic inversion data, three-dimensional structural modeling and drilling data of the lithology properties of the formation, the virtual/actual drilling lithology data is used as the calculation unit, and the sandstone thin interlayer index (STI) is used as the constraint value. The developmental strength (DS), distribution position (DP) and dispersion coefficient (DC) of the well were calculated. Then, the STI is calculated by normalization, and the main source direction is determined by the results of sedimentary facies research. The STI plane distribution of the target layer is calculated by Kriging interpolation. Using the above method, the STI of the upper part of the Shahejie Formation in the Dongying Sag was calculated. Compared with the existing drilling test results, the STI of the high-yield well is mainly between 0.4 and 0.8, indicating that the STI distribution range has a guiding significance for shale oil exploration.