Abstract: Carbonation is an important factor that affects the durability of hydraulic concrete. According to the similarity of CO₂ diffusion equation and heat conduction equation, carbonization process of hydraulic concrete is simulated with the heat conduction module in ANSYS finite element software. A numerical model is established through layered method to solve the problem of different water and cement ratio in concrete. The comparison of experimental results and numerical results of carbonation depth shows that the diffusion process simulated by the numerical model of FEM is basically in accordance with the actual diffusion process of CO₂, which can provide reference for the life prediction of carbonated concrete.