The slow anaerobic reduction rate of 2,5-dichloronitrobenzene (DCNB) is a bottleneck during its biotreatment. In this study, the process and mechanism of enhanced DCNB bioreduction by a 2-amino-3-hydroxy-anthraquinone/reduced grapheme oxide (AHQ/RGO) binary nanocomposite in the presence of Shewanella oneidensis MR-1 (MR1) are reported. AHQ/RGO was prepared using a one-step covalent combination method under mild conditions, and the as-prepared binary nanocomposite was further characterized by SEM, TEM, AFM, EA, UV-Vis, XRD, XPS, FTIR and electrochemical analyses. The results of catalytic assays showed that enhanced DCNB bioreduction to 2,5-dichloroaniline could be achieved in the presence of 30 mg/L AHQ/RGO and the k (h(-1)) value of the AHQ/RGO-supplemented system is 7.7- and 4.2-fold greater than that of the control and GO-supplemented systems, respectively. Moreover, molecular studies showed that the genes encoding cytochromes and reductases (especially yceJ and azoR) play key roles during the reduction of DCNB by MR-1 cells and multiple electron transfer pathways are involved during AHQ/RGO-mediated DCNB bioreduction. In addition, a synergistic effect between AHQ/RGO and outer membrane proteins of MR-1 was confirmed by mutant assays and is likely responsible for the catalytic performance of AHQ/RGO. This work provides a potential application of strain MR-1 and AHQ/ RGO in enhancing the treatment of DCNB-containing wastewater.