Abstract: In the exploration and development of tight sandstone gas reservoirs with a low resistivity, the Archie formula and variable m index method are often used to calculate water saturation (S_w). However, the relative error is greater than 15%, and the calculation accuracy is poor. Based on experimental and well-logging data, a double water + clay mineral type conductivity model was established, and an improved Archie formula was obtained by deriving and solving the binary linear formula. The combination and optimization of water saturation parameters were carried out, and a combined parameter model was established using regression analysis code. Pearson heatmap was employed to assign weights to the calculation results of improved Archie method and combined parameter model, and a method for calculating S_w was proposed based on Pearson weight assignment. The single-well water saturation calculated by this method had a high degree of consistency with the core saturation values determined from the properties of the sealed core. The correlation coefficient R was 0.85, and the root mean square error was 4.36, which could more accurately reflect the bound water saturation characteristics of nuclear magnetic core samples. Therefore, the proposed method based on Pearson weight assignment for calculating water saturation in this article not only accurately calculates the water saturation value of tight sandstone gas reservoirs with a low resistivity but also provides a data basis for the accurate identification of low-resistivity gas reservoirs.