<P><B>Abstract</B></P> <P>In this study an effective bacterial pretreatment method was developed to improve digestibility of <I>Miscanthus</I>. Seven new bacterial isolates, which showed excellent xylanase production ability using <I>Miscanthus</I> as carbon source, were used to perform the pretreatment experiments. After pretreatment, the hemicellulose content and crystallinity index of <I>Miscanthus</I> were decreased, while the reducing sugars released from <I>Miscanthus</I> were significantly increased by 30.8–87.8% after enzymatic hydrolysis. <I>Bacillus</I> sp. G0 was selected to optimize the pretreatment parameters via response surface methodology due to its high reducing sugars released from <I>Miscanthus</I>. 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 <I>Miscanthus</I> pretreated by optimal parameters were 305mgg<SUP>−1</SUP> dry biomass. The results suggested our bacterial pretreatment approaches have great potential to increase digestibility of bioenergy crops.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Seven lignocellulolytic enzyme-secreting bacteria were isolated. </LI> <LI> Bacterial pretreatments of <I>Miscanthus</I> were performed by these bacteria. </LI> <LI> Digestibility was improved by reducing hemicellulose content and increasing CrI. </LI> <LI> <I>Bacillus</I> sp. G0 was used to further optimize the pretreatment conditions via RSM. </LI> <LI> Maximum reducing sugars of 305mgg<SUP>−1</SUP> were obtained under the optimal conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>