• A novel conductive carbon black modified lead dioxide electrode is synthesized. • The modified PbO2 electrode exhibits enhanced electrochemical performances. • BBD method could predict optimal experiment conditions accurately and reliably. • The modified electrode possesses outstanding reusability and safety. The secondary pollution caused by modification of an electrode due to doping of harmful materials has long been a big concern. In this study, an environmentally friendly material, conductive carbon black, was adopted for modification of lead dioxide electrode (PbO2). It was observed that the as-prepared conductive carbon black modified electrode (C-PbO2) exhibited an enhanced electrocatalytical performance and more stable structure than a pristine PbO2 electrode, and the removal efficiency of metronidazole (MNZ) and COD by a 1.0% C-PbO2 electrode at optimal conditions was increased by 24.66% and 7.01%, respectively. Results revealed that the electrochemical degradation of MNZ wastewater followed pseudo-first-order kinetics. This intimates that the presence of conductive carbon black could improve the current efficiency, promote the generation of hydroxyl radicals, and accelerate the removal of MNZ through oxidation. In addition, MNZ degradation pathways through a C-PbO2 electrode were proposed based on the identified intermediates. To promote the electrode to treat antibiotic wastewater, optimal experimental conditions were predicted through the Box-Behnken design (BBD) method. The results of this study suggest that a C-PbO2 electrode may represent a promising functional material to pretreat antibiotic wastewaters.