Laser is susceptible to weather when it is propagating in atmosphere. This is because the severe weather including rain, snow and fog has a great attenuation function to laser and may cause the communication to be poor. So, it is necessary to analyze the transmission effect and attenuation characteristics of laser under different weather conditions. According to the experience relations of water content and visibility in radiation fog and advection fog, the formulas for calculating the transmission attenuation of laser in atmosphere under the fog weather condition are analyzed. Three typical empirical models for fog attenuation are simulated numerically by Matlab and the relationship of the visibility in fog with the attenuation coefficient of laser is obtained.