In this study an effective bacterial pretreatment method was developed to improve digestibility of Miscanthus. Seven new bacterial isolates, which showed excellent xylanase production ability using Miscanthus as carbon source, were used to perform the pretreatment experiments. After pretreatment, the hemicellulose content and crystallinity index of Miscanthus were decreased, while the reducing sugars released from Miscanthus were significantly increased by 30.8-87.8% after enzymatic hydrolysis. Bacillus sp. G0 was selected to optimize the pretreatment parameters via response surface methodology due to its high reducing sugars released from Miscanthus. According to the optimal model, the pretreatment parameters were set as citrate buffer/G0 fermentation broth ratio at 0.34, pretreatment time at 100h and Tween-20 concentration at 1.73%. The reducing sugars released from Miscanthus pretreated by optimal parameters were 305mgg-1 dry biomass. The results suggested our bacterial pretreatment approaches have great potential to increase digestibility of bioenergy crops.