Abstract: Lignin is the only biomass material that can provide renewable aromatic compounds in nature. Due to its low activity of main structural units, it cannot achieve ideal tanning effect when directly applied to leather tanning process. In this paper, laccase was used as catalyst and 1-hydroxybenzotriazole (HBT) was used as mediator to catalyze the sodium lignosulfonate to obtain laccase/mediator catalyzed sodium lignosulfonate (OL). The molecular weight of OL was analyzed, and it was also applied in combination with aluminum sulfate to the tanning process of the pickled sheepskin. The pH in pre-tanning bath solution, the dosages of OL and aluminum sulfate in the tanning process and the tanning sequence were optimized. Finally, the physical and mechanical properties of the crust leathers were determined. The results showed that when the pH in pre-tanning bath solution was 6, the dosages of OL and aluminum sulfate were 12% and 5%, respectively and according to the preferred order of the OL tanning and the aluminum sulfate tanning, the indicators of the obtained crust leather were the best. The shrinkage temperature (Ts) of leather can reach to 82.3 ℃, and the physical- and mechanical- properties of OL combined with aluminum sulfate tanned leather had been greatly improved by comparison with leather tanned with untreated lignin combined with aluminum sulfate.