Ultraviolet (UV) spectrum has unique properties in the atmospheric tra nsmission channel,which makes a big difference in neighbor discovery algorithm design between UV and radio frequency (RF) light.Despite significant research effort on the UV physical layer,the study on neighbor disco very algorithm design at MAC layer is quite rare.In this paper,a UV directional neighbor discovery algorithm based on time division multiple access (TDMA) is proposed to adapt to the large-scale UV ad hoc network with rapid cha nges in topology.In addition to the directional transmission and reception algorithm (DTRA) as a basis,our appr oach also uses a backoff delay mechanism to avoid node conflict,and introduces a local neighbor table by neighbor judgment and maintain mechanisms to improve the adaptability of neighbor discovery process for fast no de mobility.The performances of the new and traditional algorithms are compared by simulations.The node d iscovery propability of the new algorithm is theoretically analyzed under different node speeds and backoff dela ys.Experimental results show that fully considering the characteristics of UV atmospheric transmission,the proposed algorithm can solve the problem of node conflict effectively and achieve a preferable trade-off between collision probability and neighbor discovery delay.Specifically,it can raise 45% in the node discovery propabilit y,and raise another 5% in the node discovery propability through finding an optimal backoff delay.