Aiming at the single scattering model cannot figure how the ultraviolet communication was affected by different weather. Twice scattering model was put forward combined with the atmosphere scattering theory after studying the single scattering model. Phase function for Rayleigh and Mie scattering was studied in several weather conditions. After being scattered by particles, UV’s energy density distribution was simulated, and then the performance of ultraviolet communication system was simulated combining with particle’s thickness effectively. Simulation results indicate that non-line sight of communication is realizable, and twice scattering model can be used in different weather condition. Furthermore, the attenuation of UV signal is very sharp in rain and fog, which restricts the receiver apex angle comparatively, and that it is appropriate to UV communication in good weather, under which the receiver apex angle can reach 180°. Weather factor is more important in long-distance communication.