In view of the problem that in the measurement of infrared radiation characteristics for engine tail jet, the near-field atmospheric transmittance of tail jet is difficult to measure accurately in all-direction, this paper studies a law of the influence from near-field atmospheric transmittance at different angles and distances on the infrared radiation characteristics of the tail jet in 3~5 μm band, and simultaneously finds that the atmospheric permeability in the core area of the tail jet decreases by 5.65% compared with the natural environment. With the increase of distance, the atmospheric transmittance in the tail jet area of the engine decreases rapidly, and the test distance of 25 meters and 50 meters decreases by 22.64% and 29.88%. With the increase of the test angle, the influence of the tail jet on the atmospheric transmittance decreases. The results show that this scientific research achievement can not only support the measurement of atmospheric transmittance of aero-engine infrared characteristics, but also provide data support for the evaluation of near-field atmospheric transmittance and infrared radiation of tail jet.