A novel continuous microwave irradiation(MWI) pilot-scale reactor was designed specifically forbiomass pretreatment. To test the efficiency of this reactor,MWI-assisted alkali pretreatment of corn straw (CS) wasinvestigated using a central composite design for theresponse surface methodology. With a processing capacityof 0.28 kg CS (dry matter, DM)/h, the optimal conditionswere as follows: 4.50 kW, 30 min, and 3.50% NaOH (w/v). The glucose and ethanol production from the pretreated CSwere 63.22 and 31.29 g/100 g DM, respectively. Thesevalues were 4.42 and 3.79 times higher, respectively, thanthose from untreated CS. Structural changes in theuntreated/pretreated CS were identified by analyzing itschemical composition using X-ray diffraction (XRD),scanning electron microscopy (SEM) and fourier transforminfrared spectroscopy (FTIR). In addition, the solid residuerecovery ratio was demonstrated to be an indicator of thebiomass bioconversion potential.