Abstract: White-rot fungus Pleurotus ostreatus strain 3.42 produces extracellular laccase,but no lignin peroxidase(LiP) and manganese peroxidase(MnP) are detected in the supernatant when grown in liquid culture.When 2, 2′-azino-bis(3-ethyl-benzthiazoline-6-sulfonic acid, ABTS) (0.5 mmol/L) and Cu2+(0.1 mmol/L) were used as (inducer) of laccase production,high activity level up to 1 000 and 800 U/mL was obtained respectively.Compared with other fungus laccases,the laccase had an optimal pH value 3.5,and it was stable at pH value 4.0-6.0.Optimal (reaction) temperature of the laccase was 65℃,and it was very stable in sodium acetate buffer(pH value 5.0) at reaction temperature below 50℃.The laccase oxidized p-methoxyphenol faster than guaiacol.The laccase was strongly (inhibited) by sodium azide.In addition,anthraquinone dye Remazal Brilliant Blue R(RBBR) can be directly (decolourized) by the laccase(30 U/mL) at decolorization rate 70% after 12 h treatment.When ABTS(5 μmol /L) was used as a mediator of laccase,the dye could be completely decolourized.