Using the systematical process for isolation and purification of xylanase from Pseudomonas flu. with the tehnique (NH) 2SO 4 fractionation and Sephede x G100 gel column, we obtained the xylanase showing homogeneity in the gel electrophorosis.The melecular weight was 33?000 by SDS polyacrylamide.The optimum pH,temprature were 6.0 and 60?℃,respectively.The studies of enzyme kinetics showed K m=4.76?mg/mL.