Abstract: The hydrolysis end products of beechwood xylan, which were released by sulfuric acid or enzymes and then labeled at their reducing ends with 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization, were analyzed by HPLC assisted with MALDI-TOF-MS. Some of the hydrolysates, which were lack of related commercial available standard substances, were determined. It was found that the xylose and 4-O-methyl-glucuronic acid-xylose (B2) were the main products with minor amounts of 4-O-methylglucuronic acid (B1) in the hydrolysates of beechwood xylan by sulfuric acid. Recombinant endo-β-1,4-xylanase AnXyn10C released xylose, xylobiose, and 4-O-methyl-glucuronic acid-xylotriose (B3) as the main hydrolysates from beechwood xylan, whereas recombinant endo-β-1,4-xylanase HoXyn11A released xylose, xylobiose, xylotriose, 4-O-methyl-glucuronic acid-xylotetrose (B4) and -xylopentaose (B5), and aldohexaouronic acid. These results revealed that HPLC assisted with MALDI-TOF-MS based on PMP derivatization was a very useful and robust method for the determination of products in hydrolysis of xylan.