Corncob is rich in xylan and is a good material for producing xylose or xylitol. Xylose concentration and purty of hydrolysate will affect the quality and yield of product. This paper deals with the research on the hydrolysis of individual sugars in the easily hydrolysable polysaccharide and kinetic studies of xylan hydrolysis. It has been noticed that the total content of non-xylose sugars is as high as 28% of the easily hydrolysable polysaccharide. However, when corcob was hydrolyzed in 1.0 % H2SO4 at 80 C for 120 min,71 % non-xylose sugars in the easily hydrolysable polysaccharide were removed, and 94% xylan in the same fraction was remained. Data of xylose yield, furfural produced and xylan remaining under various hydrolysis conditions showed that the rules of stationary batch case and first-order reaction model can fit the removal of xylan. The hydrolysis rate constants (min~1) of xylan part Ⅰ and part Ⅱ were expressed respectively as follows: