Abstract: NaOH pretreatment was employed in order to improve anaerobic biodegradability and biogas yield of corn stalk. Corn stalk was first treated for 30 days at ambient temperature by sodium hydroxide (NaOH), NaOH amount added was 8% of dry matter of corn stalk. The untreated and NaOH-treated corn stalks were then anaerobically digested at mesophilic temperature (35℃) in batch reactors. For each corn stalk, four loading rates of 35, 50, 65 and 80 g/L were used. The results showed that NaOH pretreatment could significantly improve the biodegradability of corn stalk and increase biogas yield. The total biogas yield of NaOH-treated corn stalk was increased by 13.1%, 39.8%, 48.3%, and 47.8% over the untreated one for the loading rates of 35, 50, 65 and 80 g/L, respectively. The loading rates of 35 and 65 g/L achieved the highest biogas yield per gram of TS(total solid) loaded, for untreated and NaOH-treated corn stalk respectively. The contents and dry matter of main compositions of the corn stalk were changed significantly through NaOH pretreatment, approximate 1/2～2/3 of lignin, cellulose, and hemicellulose decomposed were converted into readily biodegradable soluble compounds. The biogas yield per gram of TS and VS(volatile solid) loaded for NaOH-treated stalk were increased by 13.1%～48.3% and 23.0%～61.3%, respectively, as compared with the untreated one. The average biogas yield per gram of VS reduced was the same for both untreated and NaOH-treated corn stalk, but not for the average biogas yield per gram of TS reduced. The results provided useful information for large-scale anaerobic digestion of corn stalk for production of renewable bioenergy and reduction of pollution associated with corn stalk.