Sweet sorghum bagasse (SSB) was steam-pretreated at various temperatures, residence times and SO 2 impregnation dosages. A 2 3 factorial experimental design was employed to investigate the effects of temperature, residence time and SO 2 impregnation and their interactions on enzymatic hydrolysis and ethanol production. The results showed that temperature, residence time, SO 2 impregnation and the interaction of residence time and SO 2 impregnation significantly affected enzymatic hydrolysis in an order of residence time>temperature>SO 2 impregnation>the interaction of residence time and SO 2 impregnation. Both of water-soluble and water-insoluble fraction derived from steam pretreatment were used for ethanol production, respectively. The results indicated that the effects of mentioned factors and their interactions on total ethanol yield were not significant. However, 200°C, 7.5min and 2.5% SO 2 impregnation could be determined as a group of optimal pretreatment conditions, in which the highest ethanol yield of 15.3g/100g SSB (dry basis) could be obtained without pentose fermentation.