The variation of infrared atmospheric transmittance based on atmospheric models in typical regions of China as a function of month is analyzed in this paper by using the combined atmospheric radiative transfer (CART) software.The relative errors of the results of averaged transmittance calculated with approximate foreign atmospheric model are also investigated.The results show that the average transmittance in typical regions of our country varies greatly with months.The transmittance in summer is smaller than in winter by a factor of more than 10,the difference of infrared transmittance between two close months may be about 10%;the relative errors of results calculated using approximate foreign atmospheric model can be larger than 50%.These results also illustrate that the atmospheric models of our country must be considered for the better estimations of the atmosphere transmittance,in the study of atmosphere remote sensing,radiation measurement of target,simulation of image,design of optic-electronic engineering etc.