The relative effect between combined antibiotic and anaerobic digestion (AD) is poorly understood. This study evaluated the effect of antibiotic removal during AD and the combination of florfenicol, tylosin and tilmicosin on the performance of AD and examined the ways in which these antibiotics impact the microbial community. Results showed that at same initial concentration, the removal rates of florfenicol and tylosin under combined antibiotic condition were no less than those under individual antibiotic condition. However, the removal rates of tilmicosin under the combined antibiotic condition were less than those under the single antibiotic condition. Moreover, the combined antibiotic effect on AD was different with individual antibiotics, the combined antibiotic had a marginal negative effect on AD, and methane production increased with the decrease in antibiotic concentration. The combined antibiotics negatively influenced bacterial and archaeal community in AD. Clostridia and Methanomicrobia were the most abundant bacterial and archaeal taxa, respectively. (C) 2019 Elsevier Ltd. All rights reserved.