In the field of wireless ultraviolet non- line- of- sight communication, atmospheric scattering and the angle of transceiver are important factors thoes affect the ultraviolet (UV) communication system performance. Based on the single scattering model of UV non- line- of- sight (NLOS) communication, a signal noise ratio (SNR) and channel capacity estimation method of UV NLOS communication is proposed. Then the estimated SNR and quantum- limited SNR as well as their channel capacities are calculated respectively. Comparing between two simulation results, the correctness of the method is verified. In addition, the path loss and channel capacity of UV NLOS communication under different angles of transmitter and receiver are simulated by using computer. Channel capacity under different background noise conditions is also analyzed. The simulation results show that transmitter elevation angle, receiver elevation angle and receiver field of view angle (FOV) have a great influence on the path loss and channel capacity of UV communication. Conversely, transmitter beam divergence angle has little impact on them, and channel capacity decreases as background noise increases.