Abstract: Production of xylo-oligosaccharide from corncob xylan by selective xylanase hydrolysis was investigated. The generated difference between the enzymatic hydrolysis of two kinds (dry powder and wet paste) of xylan was compared, and for explanation some possible reasons were discussed in this paper. The results indicated that the suitable technology of enzymatic hydrolysis for xylo-oligosaccharide production was as follows: using wet xylan as substrate, xylan concentration 20-40 g/L, enzyme dosage 1% (volume ratio), pH value 4.8, hydrolytic temperature 50℃, reaction time 4 h. During hydrolysis of xylan,different structural features of dry and wet xylans possibly led to different accessibility of substrate and enzyme adsorption, which resulted in remarkably different oligosaccharide yields. The results showed that the highest xylo-oligosaccharide yield was 40%, with dry xylan as substrate, 10% enzyme dosage and 12 h hydrolytic time, while only 1% enzyme dosage and 4 h hydrolytic time were demanded by the wet one to obtain the same oligosaccharide yield.