Abstract: The xylooligosaccharide solution was prepared by enzymatic hydrolysis of hemicellulose and this solution was decolorized on the HAC type powder active carbon(AC) by adsorption,the effects of the active carbon dosage and the initial total reductive sugar (TRS) concentration of xylooligosaccharide on the adsorption decolorization were experimentally studied.The experimental results showed that there was a little of coloring matter in xylooligosaccharide solution to be inaccessible to AC,and the others might be either linear or plate molecule structure which was adsorbable to AC.During the adsorption decolorization of xylooligosaccharide on AC,the adsorption rate of coloring matters was larger than that of xylooligosaccharide.In the saccharide components of the xylooligosaccharide solution,the adsorption rate of xylopentaose was the largest,that of xylotetraose was the larger and that of xylose was the smallest,which showed that the pore structure of this AC was preferable to the molecules of xylopentaose and xylotetraose.It was concluded that the adsorption isotherm of coloring matter on AC belongs to Langmuir type and the adsorption isotherms of xylooligosaccharides might be High type.Raising the AC dosage could increase both adsorption rates of xylooligosaccharide and coloring matter,and there was a linear relationship between the adsorption rate of xylooligosaccharide and the AC dosage but it was not so for the coloring matter.The adsorption rate of coloring matter could reach the highest rate 89.9% and the adsorption rate of xylooligosaccharide was 14.7% at 2.5 g/L AC dosage and 16.0% TRS of xylooligosaccharide.