Abstract: To study the effects of alkaline ozone pretreatment on enzymatic hydrolysis, composition and the surface morphology of rice straw, alkaline ozone pretreatment and enzymatic hydrolysis of rice straw , and the scanning electron microscopic analysis and the component analysis of untreated and treated rice straw were performed, The solutions from the pretreatment were examined by UV/VIS-spectrophotometer. The results showed that lignin of rice straw was oxidative degradated to small molecular organic acid by alkaline ozone pretreatment. Alkaline ozone pretreatment dropped the content of lignin and increased the content of cellulose of rice straw. The scanning electron microscopic analysis showed that mechanical tissue of rice straw was fully emerged and the porosity was increased. Thus, the effective specific surface area available to enzymatic hydrolysis of rice straw increased. The maximum yield of reducing sugars from rice straw was 902 mg/g by alkaline ozone pretreatment and enzymatic saccharification (45℃, pH 5.0, 120 h) using 31.2 mg/g enzyme, and the ratio of enzymatic saccharification was 92.57%. The enzymatic saccharification ratios of the alkaline pretreated and untreated rice straw were 74.90% and 53.53%, respectively, at the same enzymatic saccharification condition. The enzymatic saccharification ratio of the alkaline ozone pretreated rice straw was higher evidently than the alkaline pretreated and untreated rice straw.