Abstract: Due to the additional conductivity of clay minerals, oil reservoir resistivity decreases obviously in argillaceous siltstone reservoirs, which gives a great uncertainty for the calculation of oil saturation. A combination of the actual data of the 3rd member of Funing Formation in the SHW area of North Jiangsu Basin allowed some key factors of the Waxman-Smits model, such as the equivalent conductivity (B) and the exchange concentration (Q_v) of cations, to be corrected with a large amount of experimental data. A detailed quantitative evaluation of reservoirs was carried out with the corrected oil saturation interpretation model. Compared with the conventional Archie formula, the accuracy of oil saturation calculation was greatly improved, which gave a good solution to the problem of the identification of argillaceous siltstone reservoirs, and provided a reference for the determination of old field potential.