By screening inhibitory activities on the melanin polymer biosynthesis in B-16 mouse melanoma cell lines, MeOH extract of Phellodendri Cortex was found to have inhibitory effect on melanin polymer biosynthesis. Twelve compounds were isolated from the MeOH extract of P. Cortex. They were identified as obacunone (1), limonin (2), ${eta}-sitosterol$ (3), bis(2-methylheptyl) phthalate (4), cycloeucalenol (5), berberine (6), palmatine (7), jatrorrhizine (8), syringin (9), umbelliferone (10), rutaecarpine (11) and scopoletin (12) by comparison of their physical and spectral data with those of authentic samples. Among the isolated compounds, berberine (6) and palmatine (7) showed potent inhibitory effect on the melanin polymer biosynthesis in cultured B-16 mouse melanoma cell lines, with Inhibition rate of 96% and 90%, respectively. As a positive control, arbutin exhibited an inhibition rate of 56%.