Abstract: Bagasse was pretreated with methods of acid, alkaline, alkaline after acid and acid after alkaline, and the effects of different pretreatment methods on composition and enzymatic hydrolyzation of bagasse was studied.The results show that the pretreatment of bagasse with alkaline is efficient in removing lignin, while the pretreatment with acid shows no obvious effect on lignin removal. The hemicellulose of bagasse is easier to be hydrolyzed after pretreated by alkaline, and the hydrolysis rate is increased by 20% compared with that without pretreatment. The pretreatment of bagasse by alkaline after acid can not only make full use of the sugar obtained by the acidolysis of hemicellulose, but also improve the enzymolysis of the cellulose of the bagasse. Therefore, the pretreatment by alkaline after acid is a good choice for the bagasse.