Abstract:The coupling characters of cross diffusion among heat, water vapor and contaminant gas in building room were analyzed according to the non-equilibrium thermodynamic theory. Cross diffusion relationship of heat, water vapor and contaminant gas mass transfer and influence of temperature distribution on cross diffusion level were obtained. The cross diffusion characters and level under different temperature distribution were discussed, for diverse relative humidity and contaminant gas concentration in building room. The results show that water vapor and contaminant gas mass grads are less than zero when temperature grads and thermal diffusion coefficient are both positive/negative, otherwise the two mass grads are more than zero. And the higher the initial humidity and contaminant gas concentration are, the greater the absolute values of water vapor and contaminant gas mass grads are for the same temperature grads and thermal diffusion coefficient, and influences of initial humidity and initial contaminant gas concentration levels on the two mass grads are remarkable.