Laser directional jamming is the most effective way to countermeasure infrared imaging seekers. Therefore, the research on laser directional jamming to infrared imaging seekers is of significance. There are many factors affecting the jamming effectiveness of mid-wave infrared laser directional jamming. Among those factors, the power density of laser falling on a target is the important affection factor. In view of the attenuation function of atmospheric transmission for mid-wave infrared laser, the optical gain of seeker''s optical system to the mid-wave infrared laser and the variation of jamming laser spot size with distance, the relationships of atmospheric transmission of mid-wave infrared laser with atmospheric visibility and transmission distance are studied. The affection of atmospheric turbulence on the total divergence angle of laser transmission is analyzed. The directional jamming model of 3.8 μm laser for infrared imaging seekers is obtained. The relationship curves among the power density of laser falling on a target, the atmospheric visibility, the atmospheric turbulence intensity and the jamming distance are drawn. The model is verified in outdoor. The result shows that it has an error greater than one order of magnitude which mainly results from the calculation error of far field laser spot and atmospheric transmittance. This research is of a certain referential value to the development of jamming equipment.