The availability of atmosphere laser communication systems in dependence on weather conditions and on atmosphere laser link parameters, such as transmitted optical power, beam divergence, or link path distance, is discussed. A number of phenomena in the atmosphere, such as fog, can affect beam attenuation. In this work, the analysis and simulation of the empirical models (like Kruse, Vasseur, etc) indicate that the predicted attenuation of those models is similar and the main attenuation factor of 532nm laser propagation in atmosphere is aerosol particle. Attenuation caused by fog, which can be expressed as a function of the link distance, wavelength, and meteorological visibility, is calculated from visibility data collected at several locations in Guilin. Statistical evaluation of the attenuation caused by fog and the power link margin calculated from atmosphere laser communication link parameters are used for calculating the link availability.