<p>As the sole skeletal material in a blast furnace, the degradation behavior of coke significantly impacts permeability and energy consumption during smelting. In this work, a model for the non-uniform degradation of coke is constructed based on the theory of reactive mass transport in porous media and a coupled iterative method. The model is centered on two core parameters: the apparent volumetric reaction rate constant and the effective pore diffusion coefficient. This model is designed to accurately evaluate the degradation behavior of coke and offers a refinement to the existing coke quality evaluation system. SEM, mercury intrusion porosimetry, and X-ray diffraction were used to characterize the evolution of the coke’s pore structure and matrix. These data were used to determine the effective pore diffusion coefficient and its changes under various conditions. The variation law of coke internal degradation reaction gradient was obtained, and the high-temperature degradation behavior and particle size distribution characteristics of coke were calculated and analyzed accordingly. The concentration of the particle size distribution is proposed as a key indicator for evaluating coke degradation. Finally, the model was validated by comparing its predictions with experimental data. The results showed a high degree of agreement between the model’s predictions and the experimental data. The model achieved reasonable prediction of the particle size distribution concentration of coke with different initial particle sizes at different degradation times. Through this model, the influence of coke quality on blast furnace permeability can be more accurately evaluated, providing a basis for optimizing the coke quality evaluation system.</p>