A transformant of Trichoderma reesei with high production of laccase was screened from 10 recombinant transformants by fermentation experiment, and the maximum laccase activity was achieved at 96 h (8.85 IU·mL-1) in shaking flask. SDS-PAGE analysis showed that the recombinant laccase had a relative molecular mass of around 68 000. The optimum temperature and pH value for the recombinant laccase reaction were 65 ℃ and 2.2, respectively. The laccase was stable at pH between 2.6 and 4.2. Approximately 70% of the initial enzyme activity was retained after incubation of the laccase at 70 ℃ for 60 min, indicating that the laccase was highly thermostable. The effects of primary factors on the decolorization of gold orangeⅡ（100 mg.L-1）were analyzed and the decolorization rate reached 90.6% in 5 h at 50 ℃, pH 3.5, HOBT concentration 2 mmol·L-1 and laccase dosage 0.2 IU·mL-1. Excellent thermostability and efficient decolorization suggest that this crude recombinant laccase can be effectively applied to decolorize the recalcitrant azo dyes from effluents.