There a serious degradation effect on reinforced concrete by chloride ion. Cracks provide a fast channel for diffusion and accelerate the failure of structural durability. Therefore, in this study, the representative volume (REV) model of cracked concrete was constructed and its equivalent diffusion coefficient was calculated by combining the influence of cracking density, interfacial roughness and orientation degree of cracks and machine vision to identify cracks. Finally, the experimental results in the literature are compared with the calculated results based on the REV model. The conclusions show that the average relative error is 1.6% under different conditions of salt freeze, and 2.9% under different initial fracture conditions after 28 times of salt freeze. The results agree well. This indicates the proposed equivalent diffusion coefficient for cracked concrete has good reliability.