Abstract: The wheat straw alkaline sulfite pulping(ASP)is hopeful to be a potential non-wood lignocelluloses biomass biorefinery process. However, ASP spent liquor utilization is a bottleneck towards the biorefinery. In the paper, the enzymolysis conditions and properties of three kinds of xylanases from Bacillus alkalophilus, Trichoderma reacei and Pulpzyme H C were investigated based on the relative polysaccharide hydrolysis rate(RPHR). The results indicated that 27.7% of the RPHR was obtained by the xylanase hydrolysis of Bacillus alkalophilus at 6.0 μmol/(mL·min)of enzyme dosage, 50% of spent liquor concentration(weight percentage), pH 7.0, 50 ℃ for 8 h. 48.5% of the RPHR was found by the enzymolysis of Trichoderma reesei at 10.0 μmol/(mL·min)of enzyme dosage, 50% of spent liquor concentration, pH 5.0, 50 ℃ for 8 h. The RPHR of Pulpzyme HC xylanase reached to 48.0% at 8.33 μmol/(mL·min)of enzyme dosage, 50% of spent liquor concentration, pH 8.0, 55 ℃ for 4 h. The reducing sugar content of ASP spent liquor reached to 11.1 g/L from 1.2 g/L by the enzymolysis of Pulpzyme HC. Pulpzyme HC was more powerful and popular comparing with Bacillus alkalophilus and Trichoderma reesei in aspects of the efficiency and industrial application conditions. The enzymolysis of polysaccharide in ASP spent liquor was benefit to the following lignosulphonate separation and utlization.