Sugarcane bagasse contains cellulose, lignin and hemicellulose, 39-42%, 20-25% and 25-27% respectively. So it is can be used as a sugar source in many processes. Lignin and hemicellulose must be removed before hydrolysis of cellulose. Several different pretreatment approaches have been studied. The purpose of this research is comparison of acid, ozone and combination of ozone-acid as pretreatment methods for improving enzymatic digestibility of sugar cane bagasse in pilot plant scale. Sugar cane Bagasse was washed and pretreated by sulfuric acid (BA) 0.1 %, sodium hydroxide (BSH) 0.1% and (BS) steam was done at pressure 2 bar. Sugar cane bagasse was also treated by sulfuric acid (1, 2, 2.5, and 5%) at 121 ºC and 151 ºC. Ozone and ozone-acid methods also was used for delignification of bagasse. Particle diameter of bagasse in all pretreatment methods was 3-4 mm. All pretreated bagasse was hydrolyzed by cellulose enzyme complex and beta-gluocosidase at pH 5 and temperature 45 ºC. Glucose and xylose content of hydrolyzed sample was analyzed by high performance liquid chromatography (HPLC). Acid is the best media for pretreatment of bagasse in comparison with steam and base. The data showed that high concentration of acid had indirect effect on yield of sugar production in hydrolysis step. Furthermore ozonolysis pretreatment of bagasse led to higher amount of glucose in comparison with acid and acid-ozone methods. Moisture content and duration of ozonation had significant effect on sugar content of hydrolyzed solution and sugar content of hydrolyzed samples was 6%.