Abstract: The fast pyrolysis of hemicellulose in wheat straw was conducted in a tubular furnace at 550℃~850℃ to examine the products distribution and its mechanism. The result show that the gas yield is the highest compared with tar and char, and increases with the increasing of temperature. The gas is mainly consisted H₂, CO, CO₂, CH₄ and hydrocarbon. The liquid products included acids, alcohols, furan, cyclopentenes and other aromatic compounds, and its relative yield changes slightly. The relative yield of char has contrary trend to that of gas. The isopropanol-extracted components remaining in the char are alcohols and other compounds with larger molecular weight.