Abstract: Atmospheric effects have a significant impact on the target characteristics of space objects. This study proposes a method for simulating the impact of atmospheric effects on infrared targets in space. An atmospheric radiation model for near-space was established, and a ray-tracing technique was employed to calculate the observation paths to Earth from simulated positions. The atmospheric radiation along the observation paths was modeled, and MODTRAN atmospheric calculation software was utilized to compute the transmittance and path radiance for each pixel in the simulated bands. These calculated values were then used for a quantitative simulation of the atmospheric influence on the target radiation transmission. Initially, the atmospheric radiation at the target location was computed using the established near-space atmospheric radiation model, followed by modeling and simulating the atmospheric effects on the Earth background at the camera position. Finally, the target image with atmospheric effects and the Earth background were synthesized to obtain complete simulation results of the atmospheric effects. The simulation results demonstrate that this method fully simulates the impact of atmospheric effects on target radiation transmission, ultimately yielding simulated results of quantitative radiation distribution for targets in near-space. The results of this study provide high-confidence data support for the quantitative analysis of target characteristics, detection, and recognition in near-space.