Hydrothermal prehydrolysis of acacia wood was conducted at various conditions and the hemicelluloses dissolved in prehydrolysate was recovered by ethanol precipitation. Conditions test design was used to optimize the pre-hydrolysis conditions for the maximum hemicelluloses recovery rate as solid phase. Then

the composition

thermal stability and structural characterization were analyzed on the recovered hemicelluloses. The optimum pre-hydrolysis temperature and time were determined to be 170℃ and 20 min

respectively. Recovery rate of 3.93% against carbohydrate content of wood chip was obtained under the optimum conditions and main composition was xylose

accounting for 75.56% in mass

and 10.71% of glucose and 7.80% of galactose were also found. The recovered hemicelluloses at 160℃/40 min

170℃/15 min

170℃/25 min and 180℃/15 min showed a same composition with the result of 170℃/20 min but a little bit difference in the content by the analysis of ion chromatography. The thermo gravimetric analysis indicated that thermal stability of recovered hemicelluloses decreased along with the improvement of prehydrolysis temperature and extension of prehydrolysis time. Linkage of acetyl group

arabinose and galactose was found on the xylan chain by the analysis of nuclear magnetic resonance and Fourier transform infrared spectroscopy.