Abstract: Fu Xiangping, Zhuang Yongcan, Wang Honglan Department of Dermatology, Quanzhou First Hospital Affiliated to Fujian Medical University, Quanzhou 362000, Fujian, China Corresponding author: Fu Xiangping, Email: fxp8398@126.com 【Abstract】 Objective To evaluate the therapeutic effect of endothelin antagonist on ultraviolet B （UVB）?induced pigmentation in guinea pigs. Methods A skin pigmentation model was established by UVB irradiation in guinea pigs. The modeled animals were divided into 3 groups to be treated with sodium chloride physiological solution （blank control group）, an endothelin antagonist （endothelin antagonist group） and arbutin （positive control group）, respectively. Before the UVB irradiation, as well as after 15? and 30?day UVB irradiation, Mexameter? MX 18 was used to detect the melanin index in the dorsal skin of guinea pigs. After 30?day consecutive treatment, melanin index, the number of melanocytes in the epidermis and melanin content were compared among the above 3 groups. Results After 30?day UVB irradiation, the melanin index in the 9 UVB?irradiated areas on the dorsal skin of guinea pigs significantly increased compared with that before the radiation （P < 0.0001）. After 30?day treatment with the 1‰ endothelin antagonist, the melanin index in the UVB?irradiated areas significantly decreased compared with that in the positive control group （P < 0.0001）. Melanin content index?1 （MCI?1） was significantly lower in the endothelin antagonist group than in the blank control group （P < 0.05）, while no significant difference in MCI?2 was observed among the 3 groups （P > 0.05）. Conclusion Topical application of the endothelin antagonist has a certain therapeutic effect on UVB?induced pigmentation in guinea pigs.