Extreme heat-moisture climate area are always high temperature and rainy. In order to accurately predict the temperature and humidity distribution in the envelope, and simulate the effects of high temperature, high humidity and high solar radiation on the envelope, a coupled heat and moisture transfer model which takes the climate condition of extreme heat-moisture climate area into consideration is developed. The influence of solar radiation and rain load on heat and moisture transfer is considered in boundary conditions. And the changes of moisture content are taken into account in the material parameters. And a solution method based on computer soft,COMSOL and MATLAB,is proposed to solve the coupled heat and moisture transfer model simply. The COMSOL recommended setting is as follow:the relative tolerance is 0.001; the absolute tolerance is 0.0001; the mesh must be set to very fine. The numerical results of this model agree well with HAMSTAD benchmarks.