Changes in the dissolvability of hemicellulose in the Eucalyptu citriodora with relation to prehydrolysis temperature and duration in the process of water prehydro-lysis were studied. Effects of temperature and duration of prehydrolysis on the yield, pentosan contents in prepydrolyzed wood chips as well as the reducing substance contents in the solution are represented by regression equations. Accordinng to the results and the regression analyses the optimal process conditions for water prehydrolysis of Eucalyptu citriodora chips are as fellows: The ratio of water to chips 4 to 1, the highest temperature 160-165C and the reaction duration 12 hours. Sugar contents in the prehydrolysis solution were analysed by gas chromatography, which shows that the xylose, arabinose and glucose contents are 86, 4 and 10% respectively. In addition, the utilization of xylose solution and the production of mechanical pulp, chemical pulp for paper and dissolving pulp from prehydrolyzed chips are also discussed.