Abstract: The chemical structure of hemicellulose isolated from sugarcane bagasse was characterized by FT-IR，1H-NMR，13C NMR and ion chromatography. The pyrolysis characteristics and kinetics of hemicellulose at different heating rates were studied by thermogravimetric analysis (TG) coupled with Fourier transform infared spectromotry (FTIR). Results show that sugarcane bagasse hemicellulose are composed mainly of L-arabino-D-xylans with minor quantities of galactose，glucose，glucuronic acid and glacuronic acid，which is a typical structure of straw hemicellulose. The pyrolysis process of sugarcane bagasse hemicellulose can be divided into four stages，and the major reaction stage takes place between 200 to 315 ℃ with a shoulder-shaped peak at about 230 ℃. The pyrolysis remnants of coke have a higher proportion about 20% at 700 ℃. The pyrolysis kinetics can be simplified as a first-order reaction and the activation energies at different stages are 118 kJ/mol，50 kJ/mol，144 kJ/mol and 34 kJ/mol，respectively. During the hemicellulose pyrolysis process，the free water released out firstly，followed by the depolymerization and dehydration. The fission of glucosidic bond and carbon-carbon bond produce hydrocarbons，alcohols，aldehydes，acids etc.，which may decompose further into CO2，CO and other gases. FTIR analysis showed that the gaseous products are mainly vapor，CO2，CO，CH4 and other small-molecule compounds.