Abstract: As the extension of the microwave and millimeter-wave, the terahertz wave provides much greater communication bandwidth and capacity than millimeter wave. The THz pulses appeare the temporal and spatial deformation because of the waves scattered by the incident particles, and the pulses signal attenuation occurs. Based on the Mie theory, using the discrete distribution of particles with the random wave transmission and scattering theory, the extinction coefficient of fog droplet in the THz wave is calculated. Considering the fog particle spectral distribution, we obtain the average scattering characteristics with different incident wavelengths. The multiple scattering property of the THz signal from advection fog, e.g. the transmissivity and reflectivity, is investigated with Monte Carlo method. The forward and backward scattering intensities with the scattering angle by different visibility are analyzed. The result shows that in the atmospheric environment with a lower visibility, the absorption and attenuation caused by fog in terahertz wavelength can not be ignored. The research in the paper is of great significance to the space transmission and communication application of the terahertz technology.