In order to effectively improve the channel transmission efficiency of optical communication systems, a research on channel modeling of free space optical communication systems in time-varying environments is proposed. This method is based on the analysis of atmospheric scattering and attenuation characteristics during signal propagation in optical communication systems in a time-varying communication environment. Using the atmospheric scattering coefficient and atmospheric attenuation coefficient as constraints, combined with the channel characteristics of the optical communication system, obtain the distance between the light source and receiver of the optical communication system, and calculate the signal power at the receiving end of the system. Establish a channel impulse response function based on the above constraints and parameters such as distance and power, and establish a channel transmission model for free space optical communication systems. The experimental results show that the method has a good fitting effect with the actual channel, and the channel model efficiency is as high as 0.9 or above. The channel model performance of this method is relatively high.