Abstract: The lignin from jute fiber was extracted with dioxane/water solution, followed by laccase treatment. The molecular weight change of lignin was investigated by Gel permeation chromatogram(GPC), and structural changes were researched by FTIR, elemental analysis and 1H-NMR. The results show that the number average molecular weight and weight average molecular weight of laccase-treated lignin are increased，while the content of phenolic hydroxyl group is decrease. The phenolic lignin is polymerized during the laccase treatment and its molecular weight distribution becomes wider. The content of syringyl units is decreased, while the content of aliphatic hydroxyl group, total hydroxyl group and carbonyl group are increased after laccase treatment.

Key words: laccase, jrte fiber, lignin, structure