<p>Antibiotics make their way into aquatic ecosystems through multiple routes, and due to their ecotoxicity, they can negatively impact the treatment effectiveness of conventional pollutants in wastewater. However, the overall pollutant removal performance and rhizosphere microecology changes in bioretention cells (BRCs) under combined antibiotic stress have rarely been reported. In this study, ofloxacin (OFLX) and tetracycline (TC) were identified as focus antibiotics, and <i>Phalaris arundinacea</i> was chosen as the plant to explore the overall contaminant removal capacity and rhizosphere microecology response of BRCs under combined antibiotic stress. Additionally, the mechanisms of root exudates from <i>Phalaris arundinacea</i> in response to combined antibiotic stress were analyzed. It was found that the pollutant removal performance of BRCs under combined antibiotic stress was effective, with average removal rates of over 98% for total phosphorous (TP), over 70% for total nitrogen (TN) and ammonia nitrogen (NH₄⁺-N), and over 90% for chemical oxygen demand (COD), OFLX, and TC. With increasing concentrations of combined antibiotics, bacterial richness and the total number of species significantly reduced. The bacterial community structure was similar between R1 and R2, as well as between R0, R3, and R4. Acetic acid was significantly and positively correlated with citric acid secretion, and lactic acid worked synergistically to resist antibiotic stress. Tartaric acid and maleic acid regulated the composition of bacterial species and thereby influenced the degradation of pollutants. This research enhances the understanding of the biological processes of antibiotic wastewater treatment by BRC.</p>