Using the experimental data of mercury compression, Swanson constructed a Swanson curve characterizing the change of cumulative seepage capacity of the pore throat during the whole process of mercury compression by taking the mercury saturation as the independent variable and the ratio of mercury saturation to mercury pressure ( \(S_{Hg} /P_{c}\) ) as the dependent variable, and the reservoir was divided into two types of pore throat systems, namely, large and small pore, based on the vertices of this curve. However, Swanson curve can only reveal the cumulative seepage characteristics of the pore throat, but not the interregional seepage characteristics. Therefore, the reservoir pore throat system dichotomy scheme is coarser. Therefore, drawing on the idea of Swanson curve to identify pore-throat system, a new mercury compression efficiency curve was constructed to characterize the change of see-through capacity in the pore-throat interval during the whole process of mercury compression, with the mercury saturation as the independent variable and the mercury compression efficiency ( \(\Delta S_{Hg} /\Delta P_{c}\) ) as the dependent variable. According to the variation rule of the curve and its two seepage mutation points, the reservoir is divided into three types of pore throat systems: large pore, medium pore and small pore. The case analysis proves the validity of the proposed delineation method, and the pore fractal characterization further verifies the reliability of the delineation results. The study presents a three-part scheme of reservoir pore throat system and its division method, which improves the recognition accuracy of reservoir pore throat system and is of great significance for deepening the understanding of reservoir pore throat heterogeneity and evaluating the quality of reservoirs.