The kinetics of enzymatic hydrolysis of rice straw pretreated by a bio-based basic ionic liquid (choline hydroxide) under ultrasound was investigated. The structural characterization of rice straw before and after the pretreatment was performed with EA, HR-XRD, AFM, and FPA-FTIR, by which the increase of crystallinity, the destruction of surface structure, and the changes in functional groups and compositions were observed after the pretreatment on rice straw with choline hydroxide under ultrasound, thus significantly enhancing the enzymatic hydrolysis by cellulase. A simplified kinetic model with the impeded reaction of enzyme was developed to successfully describe the enzymatic hydrolysis of rice straw in a heterogeneous system. Based on the experimental observation, a time-dependent decay coefficient for the impeded reaction was proposed. The initial observed rate constants as well as ineffective coefficients were obtained to elucidate the interaction of enzyme and substrate, and the applicability of the simplified model was demonstrated. (C) 2015 Elsevier Ltd. All rights reserved.