<p>To better study the seepage law of tight rocks during triaxial compression experiments, it is necessary to establish a permeability evolution model with simple structure based on the traditional fractal capillary seepage model. Firstly, the definition of porosity in the fractal capillary seepage model is improved, and the transformation relationship between fractal capillary model and fractal geometry is proposed. Meanwhile, a new generalized Sierpinski carpet is introduced, providing a simpler and more intuitive method for analyzing porosity evolution. Subsequently, taking the fractal dimension as an inherent property of rocks, the evolution mechanism of fractal units under this condition is elaborated in detail. To ensure that the aperture distribution consistently conforms to the normalization condition, the fractal scaling relationship of capillaries is improved, and on this basis, a fractal-based permeability evolution model is established. In addition, the evolution laws of various microstructural parameters with stress are further analyzed. This analysis enables the permeability evolution model to rely on effective stress for application in triaxial compression experiments. Meanwhile, the relevant parameters are also constrained by volumetric strain. Finally, the model is fitted using publicly available experimental data from low-permeability sandstone and Beishan granite, verifying its applicability to tight rocks.</p>