Abstract: The membrane fouling and its reversibility during ultrafiltration of xylan extractives were invesiigated, and the method to clean the fouled membrane was examined. It was found that lower transmembrane pressure and higher feeding velocity were favorable to alleviate the membrane fouling, that 4% NaOH solution could efficiently recover the solvent flux through the membrane, but backwash could only regain the part of the solvent flux.