The enzyme is produced by submerged fermentation of Bacillus subtilis followed by purification and formulation, and contains endo-1,4-beta-D-xylanase activity. The product can effectively hydrolyze xylan in between cellulose fibrils into soluble smaller molecular products, loosening the fiber structure and improving Permeability of cellulosic materials. Alkaline xylanase can be used for enzymatic treatment of straw, wood, bamboo, Chinese herbs, tobacco and feed.