Atmospheric transmittance is an important factor affecting the radiation measurement precision. Generally, the error of conventional atmospheric transmittance calculated from atmosphere parameters by using a atmosphere model calculation software such as MODTRAN is above 15%, which limits the target radiation measurement precision greatly. Therefore, a new radiation measurement method was proposed, by which the ratio between the really-measured atmospheric transmittance and the calculated one for a distance was taken to obtain an atmospheric transmittance correction coefficient. Then, the correction coefficient was used to correct atmospheric transmittances of other measurement distances. Experiments show that the precision of the corrected atmospheric transmittance is better than 8.1%,which improves the target radiation measurement precision greatly. A radiation measurement experiment was performed by using a midwave infrared camera and a blackbody, and the results show that the radiation inversion precision obtained by the conventional method is about 20% and the precision obtained by the proposed method using the corrected atmospheric transmittance has been better than 10%.