Abstract: In order to study the enhancement of acid hydrolysis process of plant fiber in BmimBr ionic liquid medium by the microwave irradiation heating, the microwave irradiation promoting acid hydrolysis of straw pole and preparation the reducing sugar were determined with the BmimBr ionic liquid as reactive medium in this paper. The influences of ionic liquid volume, microwave power, irradiation time, sulfuric acid concentration, reaction temperature on yield of reducing sugar with acid hydrolysis of straw pole were mainly tested. The results indicated that the best condition of acid hydrolysis of straw pole into reducing sugar in microwave irradiating was 10.0% H2SO430.0 mL, BmimBr 10.0 mL, reactive temperature 85℃, irradiation time 45 min, microwave power 500 W, and the yield ratio of reducing sugar reached 22.94% at the best condition, but the yield ratio of reducing sugar at the conventional acid hydrolysis was only 14.50%. It is clear that the yield ratio of reducing sugar in the straw pole by microwave irradiation promoting acid hydrolysis was higher than the yield ratio of reducing sugar by the conventional acid hydrolysis. So the microwave radiation could promote acid hydrolysis of plant fiber and significantly shorten the time of saccharification and raise the yield ratio of reducing sugar in the ionic liquid medium.