The modified anaerobic baffled reactor (MABR) is a type of anaerobic baffled reactor (ABR) with improved design concepts and principles. Residence time distribution (RTD) analysis at hydraulic residence times (HRTs) of 12, 16, 20 and 24 h was performed to investigate the mixing patterns and dead space. The BioWin computer modeling software was developed to simulate the performance of the reactor. The model was calibrated using values from experimental runs at HRTs of 12, 16, 20 and 24 h and validated with experimental runs at HRTs of 8 and 10 h. The results of a hydraulic characteristics study showed that the mixing patterns for all test conditions fell between plug flow and completely mixed and the longer the HRT was, the closer the mixing pattern was to plug flow. However, a negative correlation between the dead space and the mixing pattern was observed, the longer the HRT was, the greater the dead space was. The simulated values of effluent chemical oxygen demand (COD) concentration, effluent total suspended solids (TSS) concentration, biogas flow and effluent pH value were predicted with the measured values by absolute relative errors (AREs) of less than 11.7%, 12.4%, 12.9% and 4.3%, respectively, for all test conditions. The model successfully characterized the biomass characteristics in the reactor illustrate that BioWin can well reflect the actual operating performance of the MABR. (C) 2015 Elsevier B.V. All rights reserved.