Abstract: Polyphenols and their tyrosinase activity in the leaves of Castanopsis calathiformis were sludied. The 80% methanol extract of C. calathiformis leaves was separated and purified by Chromatorex C18, Toyopearl HW-40F, Sephadex LH-20 and other column chromatography methods. The structures of compounds were determined according to the NMR data and literature comparison, and the isolated principal components were screened for their tyrosinase inhibitory activity. Eighteen compounds were isolated and identified from the C. calathiformis leaves, including 9 phenolic acid compounds, 3 ellagitannins and 6 flavonoids, which were identified respectively as protocatechuic acid(1), gallic acid(2), (Z)-p-hydroxy-cinnamic acid(3), (E)-p-hydroxy-cinnamic acid(4), 3-O-galloyl-shikimic acid(5), 4, 5-di-O-galloylquinic acid(6), 1, 3, 5-tri-O-galloylquinic acid(7), 3, 4, 5-tri-O-galloylquinic acid(8), 1, 3, 4, 5-tetra-O-galloylquinic acid(9), 2, 3-O-(S)-hexahydroxydiphenoyl-β-D-glucopyranose(10), punicacortein A(11), pterocarinin A(12), quercetin(13), myricetin-7-O-D-galacopyranoside(14), kaempferol-3-O-β-D-xylopyranosyl(1→2)-β-D-glucopyranoside(15), myricetin-3-O-D-glucopyranoside(16), myricetin-3-O-(6″-galloyl)-β-D-galactopyranoside(17), myricetin 3-O-(2″-galloyl)-β-D-galactopyranoside(18). All compounds were isolated from C. calathiformis for the first time. The results of tyrosinase inhibitory activity screening showed that compounds 2, 8, 12 and 13 had a certain inhibitory effect on the activity of tyrosinase. Compound 13 had the best inhibitory effect on the activity of tyrosinase, and the half inhibitory mass concentration(IC₅₀) value was 0.420 g/L±0.08 g/L(IC₅₀ value of positive control kojic acid was 0.099 g/L±0.01 g/L).