The production of xylanase (TrxA) by Trichoderma reesei JL-1 in solid-state fermentation (SSF) was optimized by response surface methodology (RSM). Results revealed that factors of concentration of added ammonium sulfate, and moisture content had significant effect on the TrxA production (P<0.05). The maximum xylanase activity (485.0 U/g U/g dry fermentation product) was obtained at 2.9% the ammonium sulfate by employing wheat bran as the solid substrate, 61.6% moisture content and 59.5-h fermentation, which was close to the predicted one, and was 1.8 times as high as that of the basic medium. The optimum temperature and pH for TrXA activity were 45°C and pH 5.0, respectively. Over 90% of xylanase activity was retained after treatment of the enzyme by preincubation over a pH range of 3.0-5.0 for 1 h at 25°C. TrxA exhibited Km and Vmax values of 1.458mg/mL and 25.316 μmol/min/ml, respectively. In the presences of metal ions such as Mn2+the activity of the enzyme increased. Whereas strong inhibition of the enzyme activity was observed in the presences of Fe3+ and Ca2+.