The saccharification of crop straw by hydrolysis was carried out under the condition of microwave radiation with the dilute sulfuric acid. The amount of sulfuric acid, the ratio of liquid and solid, the microwave radiation time, the pressure, and the power on the yield of reducing sugar were investigated. The experimental results show that the yield of reducing sugar increased at first and then declined with increasing of the experimental conditions．It was determined that the yield of reducing sugar reached the maximum, 21.8% at the following conditions: the amount of sulfuric acid is 2%, the ratio of liquid and solid is 15.0, processing time is 40 min, the pressure is 0.3 MPa, and power is 225.0 W.