A coupled heat, air and moisture transfer model， which takes into consideration the heat transfer, moisture transfer and air convection and their coupled effect, was developed to predict the distribution of the temperature and humidity and to investigate the rule of the coupled heat, air and moisture transfer in walls. The temperature, relative humidity and air pressure were chosen as the driving potentials. A program based on the finite element method was developed to calculate the governing equations. And the numerical results of this model were compared with the internationally accepted HAMSTAD benchmarks, and the results agree well with each other.