Abstract: The gene of xylanase(XYN II) was amplified by RT-PCR from the total RNA of Trichoderma reesei Rut C-30 and sequenced. The gene comprised an open reading frame that encoded a polypeptide of 223 amino acid residues, containing a signal peptide of 19 amino acid residues. A recombinant plasmid pPIC9K-xyn II was constructed by inserting gene xyn II into Pichia pastoris secretory vector pPIC9K. Linearized pPIC9K-xyn II was transformed into P.pastoris GS115 with the method of electroporation. The recombinant strain identified by G418 selection and confirmed by PCR analysis was induced by 1.0% methanol at 28℃ to express the recombinant xylanase, the highest enzyme activity of 1.45 IU/mL was detected for 60 h incubation. The optimal pH value and temperature of the enzyme activity is 6.0 and 50℃, respectively.