Abstract: Neosinocalamus affinis, a widely distributed grassy material rich in cellulose, is a potential resource for cellulose ethanol production. In this study, a coupled pretreatment of low-pressure steam explosion (SE) and alkaline sulfite (AS) was applied to N. affinis in order to protect carbohydrates against degradation and increase delignification, which is useful for subsequent enzymatic hydrolysis. The optimal conditions of SE-AS were explored using the orthogonal experiment. It was found that the optimum condition of SE-AS process was 140 ℃ in 40% dry substrate Na2SO3 and 15% dry substrate NaOH. A final glucose yield of 88.54% was achieved during the 72-h enzymatic hydrolysis process (substrate concentration was 5%). Further simplification by combining low-pressure SE and AS into one-step pretreatment with a similar glucose yield of 87.25% was achieved with 89.25% of cellulose retention rate.