Laccase is a polyphenol oxidase (ρ-dihydric phenol oxidase, EC1.10.3.2) containing four copper ions, belonging to the copper blue oxidase, present as a monomeric glycoprotein. Laccase exists in fungi, bacteria and plants. It mainly takes effect on phenol-like compounds, performing one-electron oxidation. The compounds include phenols and their derivatives, aromatic amines and their derivatives, biological pigments, and so on. Laccase can be used in paper industry to remove lignin from pulp or raw materials to improve pulp whiteness; it can also be used for deinking, wastewater treatment and improve the wet strength of pulp.