Abstract: The mid-infrared atmospheric transmittance and the absolute deviation were calculated with three different HITRAN databases using LBL software. Results show that the average absolute deviation of HITRAN2k and HITRAN04 decreases with the increase of initial height, the absolute deviation of HITRAN2k and HITRAN04 increases as the resolution increases. The average absolute deviation of HITRAN04 was less than the HITRAN2k at the four initial height. For example, the maximum absolute deviation of HITRAN04 and HITRAN2k was 0.338 and 0.394 with 1 cm-1 spectral resolution only considering the absorption of CO2. The maximum absolute deviation of HITRAN04 and HITRAN2k was 0.950 and 0.936 with 0.1 cm-1 spectral resolution considering the absorption of all kinds molecules. The deviation caused by old versions of the database should be considered for calculating infrared atmospheric transmittance. The difference caused by different versions of the database and spectral resolution should be considered for calculating infrared atmospheric transmittance.