Abstract: In this study,MTT assay was carried out to study the effect of different extracts from "Anti-UV Clone"(Obtained from Bupleurum scorzonerifolium Willd.callus) on the viability of human keratinocyte cells (HaCaT cells) exposure to UV-B radiation.The results showed that both ethanol and ethyl acetates extract of the cell clone inhibited the viability of HaCaT cells.However the viability of HaCaT cells was promoted by the water extract of the cell clone in a dose dependent manner,thus the water extract was chose to further assay.At a dose range of 0.05—0.2U/mL,pre-treatments and post-treatment with water extract both improved the viability of HaCaT cells compared to cells only exposed to UV-B irradiation (p0.05).When at a concentration of 0.2U/mL,pre-treatments and post-treatment with water extract can improve the cell viability by 10.54% and 14.95% respectively in respect to cells only exposed to UV-B irradiation.Thus it was concluded that the water extract of "Anti-UV Clone" probably contains UV-B protection agents.