Acquired pigmentary skin diseases such as abnormal melanogenesis, vitiligo, chloasma and inflammatory pigmentation are related to regulate the melanin production, In this study, an ethanol extract of Hovenia dulcis Thunb.(EHD) makedly inhibited melanin biosynthesis and suppressed, the protein expression of tyrosinase, tyrosinase-related protein 1(TRP-1), and tyrosinase-related protein 2(TRP-2) in B16F10 cells. On the other hand, EHD did not inhibit mushroom tyrosinase activity. These results indicate that EHD may contribute to the inhibition of melanin biosynthesis through regulating tyrosinase activity and expression, and serve as a new candidate in the design of new skin-whitening or therapeutic agents.