In this paper, the hemicelluloses extraction of bagasse with NaOH/borax was studied, and some parameters which may affect the hemicelluloses yield and properties were discussed, such as alkali charge, borax charge, liquid-to-solid ratio, temperature and time of extraction. The compositions and characteristics of hemicelluloses were analyzed by FT-IR, GC, GPC. The results showed that compared with the conventional alkali extraction, the hemicelluloses dissolution rate was increased and degradation degree of the hemicelluloses was decreased with NaOH/borax. When the alkali charge was 65%(based on NaOH)and borax charge was 7% at a liquid-to-solid ratio of 15:1 at 90 ℃ for 180 min, the dissolution rate of hemicelluloses up to 84.5% (to the hemicelluloses content in material).