Abstract: An experiment was carried out using biogas slurry and NaOH solutions different in concentration to pretreat corn stalks at 25℃ for biogas production to explore relationships of NaOH dosage with fiber structure of the pretreated corn stalk physico-chemical properties of the pretreatment solution, and energy production characteristics. Results show that 7 days after pretreatment with NaOH solution 4 mg•g^-1 in concentration, COD concentration in the pretreated material solution became basically stable, with pH ranging between 7 and 8. At that time, the material was ready to be packed into the biogas tank for fermentation. A scanning electron microscope (SEM) was used to observe changes in fiber structure of the pretreated corn stalks. It was found that the corn stalks pretreated with 4 mg•g^-1 NaOH becasme rough and porous on the surface, thus facilitating contact of anaerobic microbes with the substances, and eventually increasing biogas production by 4.5 times as compared with the use of untreated corn stalks, reaching 225.8 mL•g^-1 dry matter. Taking anaerobic digestion performance, pretreatment cost and engineering operation into consideration, the method of using 4 mg•g^-1 NaOH solution to pretreat corn stalks is easier to be etended.