n this study, the effect of NaOH pretreatment on anaerobic digestion with poplar processing residues as sole feedstock was conducted. The objective of the study was: (1) to test whether the poplar processing residues are good substrate of anaerobic digestion for methane production after NaOH pretreatment; (2) to investigate the effect of NaOH pretreatment on the daily and total methane production, and determine the optimal condition of pretreatment and anaerobic digestion; (3) to test the ef- fect of methane production with poplar processing residues as substrate of anaerobic digestion, compared to the abundant lig- nocellulosic biomass of corn straw; (4) to study the structure changes of poplar processing residues by Scanning electron microscopy (SEM), FT-IR spectra and X-ray diffraction analysis during pretreatment.