Electrical resistivity is a fundamental parameter for evaluating fluid saturation and reservoir properties in shale formations. However, existing conductivity models often exhibit limited accuracy due to the highly complex, coupled conductive mechanisms inherent to shale, which involve multi-scale pore networks, mineral surface conduction, and variable wettability. To address this limitation, this study proposes a dual-mechanism characterization model for shale conductivity. By expanding the electrochemical framework of clay surface conduction, the proposed model comprehensively integrates interconnected pore-water conduction, surface electric double layer conduction, and wettability effects. The model was validated using published multi-salinity experimental datasets from four clay-rich core samples, achieving high goodness-of-fit (R2 values of 0.954–0.981) and low mean relative errors (4.55%–7.66%). Furthermore, the model was verified against experimental resistivity measurements of two organic-rich shale core plugs from the Gulong (GL) Formation in the northern Songliao Basin, demonstrating its ability to characterize the non-Archie electrical responses of mixed-wet shales. The results confirm the model’s robust capability to precisely characterize shale electrical responses. Ultimately, this work provides a reliable methodology for quantifying reservoir parameters, thereby advancing the petrophysical evaluation of shale hydrocarbon resources.