Abstract: Objective To evaluate the effects of 308 nm monochromatic excimer light （MEL） on cell apoptosis, cycle of and KIT expression in human melanocytes. Methods Melanocytes were obtained from circumcised prepuce, and subjected to primary culture. After 4-5 passages, the cells were irradiated with 308 nm MEL at the doses of 0, 20, 40, 80, 160 and 300 mJ/cm2. After another 24-hour culture, flow cytometric analysis was used to detect the apoptosis and life cycle of these cells, real time RT-PCR and Western- blot to measure the expressions of c-kit mRNA and KIT protein in melanocytes, respectively. Results The apoptosis of melanocytes was not significantly changed after exposure to MEL at doses lower than 160 mJ/cm2, but was increased significantly by the irradiation of MEL at the dose of 300 mJ/cm2 （P < 0.05）. After exposure to 308 nm MEL at the dose of 80 mJ/cm2, the percentage of melanocytes in S phase were （29.06 ± 0.75）% , significantly higher than that in the untreated group （22.64 ± 0.07）% （P < 0.05). The expression of c-kit mRNA was significantly increased by MEL at the doses of 40 and 80 mJ/cm2, but decreased significantly at the doses of 160 and 300 mJ/cm2. The changes of KIT protein were consistent with those of c-kit mRNA after exposure to 308 nm MEL. Conclusion The 308 nm MEL at the dose of 80 mJ/cm2 can promote the proliferation of and expression of KIT protein in melanocytes, which may be a mechanism for the treatment of vitiligo with 308 nm MEL.