Abstract: Based on physical characteristics of the fog, the attenuation feature of laser propagation in the fog was investigated theoretically. The signal model, noise model and transmittance of wireless laser communication systems were presented. Based on the relation between the attenuation ratio and the transmittance of the laser, the variation of the attenuation of 10.6μm laser traveling in advection fog or radiation fog with the visibility and the FOV of the laser receiver is given. The numerical analysis results show that the performance of the wireless laser communication systems is highly dependent on laser wavelength, visibility, range and receiver FOV.