Abstract: Cellulase poor xylanases can reduce the content of fines in the light weight coated secondary fibers and increase drainage rate under appropriate enzymolysis condition.Proportion of fines in the material is 37.5% and in Cobb value is 25.86 g/m² by alkyl ketene dimmer(AKD) sizing.But content of fines is decreased to 28.4% and Cobb value to 20.03 g/m² after the material has been disposed for 30 min by xylanases.Content of fines affects AKD sizing.Size resistance of paper is improved as content of fines is decreased.The higher content of fines is in the stock,the more AKD absorbed on the fines surface.AKD is easily lost into white water so that retention rate reduces.AKD sizing effect can be improved by enzymolysis of secondary fibers.Content of fines has significant effects on AKD sizing.

Key words: cellulase-poor xylanases, alkyl ketene dimmer(AKD), sizing agent