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Total organic carbon content (TOC) is the most important parameter to determine the quality of source rocks. In order to solve the problem of low accuracy in the application of the traditional ΔlogR method to marine shale gas reservoirs with complex depositional environments, taking the marine shale gas reservoirs of Group B in Area A of Guizhong Depression as the research object, based on the analysis of the causes of low resistance in the study area, the well diameter correction of the logging curve was performed according to the range of expansion, taking the B-group marine shale gas reservoir in the Guizhong Depression A as the study object. The Th/K data from natural gamma energy spectrum logs were also used to establish a multivariate fitting relationship with ΔlogR. An improved ΔlogR method based on well diameter correction and natural gamma energy spectrum logs was proposed. The results show that after the correction of the acoustic transit time curve, the influence of the logging data distortion caused by the diameter expansion of the well was reduced. At the same time, combined with natural gamma spectroscopy logging, it can adapt to the complex geological background and strong heterogeneity of the study area, greatly improve the prediction accuracy of the total organic carbon mass fraction, and has good generalization and applicability. This method can provide a reference for the evaluation of marine shale gas reservoirs from Group B in area A of Guizhong Depression. [ABSTRACT FROM AUTHOR]