Ultraviolet (UV) communication system can provide non-line-of-sight links by exploiting atmospheric scattering of light. The analytic expression of the channel impulse response to received signals is derived and then with this expression the channel characteristic is studied. The relationships between channel lengths, inter symbol interference, bit error rate, bit rate and system geometry configuration are achieved. The results indicate that the channel bandwidth mainly rests on the attenuation coefficient, and channel capability is affected by the communication range and attenuation coefficient. Ultraviolet communication system is sensitive to system geometry configuration and has very narrow bandwidth and severe inter symbol interference. It is suitable for low bit rate, short range and secret communications.