Abstract: To enhance the pretreatment effect for production of cellulose ethanol, the influences of water immersion and CaO treatments before steam explosion on the structure destruction of corn stalks and enzymatic saccharification were studied. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were involved in this study. The results showed that compared to the control (corn stalks pretreated with steam explosion), corn stalk immersed with 30% water (mass ratio of water to corn stalk was 30:100) for 5 days, or treated with 2% CaO(mass ratio of CaO to corn stalk is 2:100) for 3days, or treated with 2% CaO and 30% water for 1 day before steam explosion enhanced the lignin degradation rate from 20.7% to 27.8%, 35.1% and 30.9%, respectively; the concentrations of reducing sugars in the three pretreatments were 3.81, 3.59 and 3.46 g/100mL respectively; and the sugar yields in the three pretreatments were 42.2%, 39.8% and 38.3% and increased by 23.7%, 16.6% and 12.3% respectively compared with the control. Pretreatment with 30% water immersion for 5 days and 2% CaO for 3 days intensified the destruction of surface structures and the degradation of lignin, the relative crystallinity of which increased by 47.0% and 54.5% respectively compared to the control(42.6%). Pretreatment with 30% water or 2%CaO exhibited high efficiency and sugar yields. It is benefit for the promotion of this technology with low-price and non-contaminating reagents.