Abstract: Accurately predicting relative permeability is an important issue in the research of multiphase flow in tight reservoirs. Existing predictive models typically rely on the capillary tube bundle model featuring circular cross-sections, often overlooking the impact of pore geometry on fluid flow behavior within reservoirs. In this work, the intermingled fractal theory of porous media is introduced to characterize the intricate local features within the internal space of tight rocks. Initially, iterative rules for diverse fractal units are skillfully designed to capture the actual characteristics of pore cross-sectional shapes. Subsequently, analytical relationships are derived between the iterative parameters and the area, wetted perimeter, and hydraulic diameter of pores generated by these units, followed by the establishment of a relative permeability model that considers pore geometry. The model’s validity is confirmed through comparisons with experimental data and published relative permeability models, with correlation coefficients exceeding 0.996. Finally, various factors affecting two-phase flow characteristics are analyzed. The results reveal that pore geometry has a significant impact on flow behavior in porous media. Assuming that the flow channels are cylindrical typically leads to an overestimation of permeability, with the maximum relative error reaching 46.91%. Additionally, the tortuosity fractal dimension is a determinant factor influencing the relative permeability of both wetting and non-wetting fluids, and the phase permeability is sensitive to variations in solid particle size and porosity. The proposed intermingled fractal model enhances the accuracy of evaluating fluid flow characteristics in microscale pore channels and offers a novel framework for simulating porous media with complex geometries.