A simple pretreatment method, NaOH swelling at a low temperature and then HCl regeneration, was developed for depolymerization of cellulose to glucose. Cellulose was transformed into amorphous hydrogel during the treatment; and due to the easy diffusion of H+ and Cl ions into the cellulose hydrogel network as well as the strong ability of Cl to disrupt the massive hydrogen bond, the hydrolysis rate was greatly enhanced. The method is effective for alpha-cellulose, microcrystalline cellulose, filter paper, ramie fiber and absorbent cotton. Even at a high alpha-cellulose concentration of 50 g/L, 29.1% yield of glucose was still obtained within 10 min at 160 degrees C under microwave irradiation, where up to 16.2 g/L of glucose solution was given. The influence of NaOH concentration, HCl concentration, hydrolysis temperature and time on the hydrolysis rate was investigated. The structure of cellulose hydrogel was also studied to confirm the reaction mechanism. (C) 2015 Elsevier Ltd. All rights reserved.