With the mass diffusion module of ABAQUS, the moisture diffusion behavior of recycled aggregate concrete material (RAC) was investigated in this work. The simulation was carried out under the standard drying conditions (Ambient humidity: H=60%; Temperature: T=20°C). The results indicate that: with the dry age grows, the water evaporation begins from the RAC’s surface first, and the water concentration reaches the equilibrium value rapidly; then the evaporation process gradually extends to the interior, but the process is quit slowly. In moisture diffusion process, the water concentration takes on gradient distribution. the calculated value of water concentration matches well with the experiment results, and can provide a theoretical base to the caculation of drying shrinkage stress of RAC.