The invention relates to konjac oligosaccharide for regulating intestinal flora, in particular to a novel method, namely a method to acquire konjac oligosaccharide mannose mixture with low molecular weight, narrow distribution, low monosaccharide content and higher purity, by means of primary alcohol precipitation and secondary acetone treatment after enzymatic hydrolysis. The method includes the steps of hydrolyzing konjac mannan by beta- mannanase to obtain konjac mannose oligomer hydrolysate, adding ethanol precipitation of certain volume into the konjac mannose oligomer hydrolysate concentrated, concentrating supernate, adding acetone of certain volume, performing centrifuging after precipitating, removing supernate, and collecting precipitation to obtain the oligosaccharide mixture mainly containing konjac mannobiose, mannotriose, mannotetraose, mannopentaose, mannohexaose and mannoheptaose. The konjac oligosaccharide prepared by the method has a certain effect in regulating the intestinal flora.