Abstract: Ultraviolet (UV) atmospheric transmission is simulated using atmospheric transmission model LOWTRAN. The working wavelength of UV communication system is confirmed numerically. Influences of visibility, geographical position, climate, distances and directions of transmission, altitudes, and weather etc. on the UV atmospheric transmittance are analyzed. The results demonstrate that the solar blind region with a center wavelength around 250 nm should be chosen as the working wavelength of the UV communication system. Seasons, zones, wind and rain have little influence on UV atmospheric transmittance in solar blind region. Exponential attenuation of UV atmospheric transmittance for the horizontal paths decides that the UV communication system works locally and safely. The UV atmospheric transmittance hardly changes vs. altitudes within 1 km above sea level.