Abstract: In view of the permeability of hydraulic concrete slab due to corrosion damage, a corrosion prediction model was deduced in this paper based on the conservation of mass from the microscopic point of view, and the relationship between the corrosion degree and permeability was explored. Comparison of numerical simulation results and experiment results showed that the impermeability of cement matrix decreased with time, and the impermeability decreasing range increased with the depth of corrosion. In the corrosion region, the decrease of impermeability presented non-uniformity, and the degradation of impermeability of cement base surface was the greatest. The impermeability of cement-based surface decreased sharply at the initial stage of corrosion, and then slowed down gradually. The impermeability of concrete face slab will decrease gradually due to the corrosion of cement base, so the concrete surface needs treatment to improve the durability of corrosion resistance.