摘要An ultrasensitive electrochemical sensor based on polydopamine/carboxylic multi-walled carbon nano-tubes (MWCNTs-COOH) nanocomposites modified glassy carbon electrode (GCE) was presented in this work, which has been developed for highly selective and highly sensitive determination of an anti-microbial drug, metronidazole. The preparation of polydopamine/MWCNTs―COOH nanocomposites/GCE sensor is simple and possesses high reproducible, where polydopamine can be coated on the surface of MWCNTs―COOH via a simple electropolymerization process. Under optimized conditions, the proposed sensor showed ultrasensitive determination for metronidazole with a wide linear detection range from 5 to 5000μmol/dm3 and a low detection limit of 0.25μmol/dm3 (S/N = 3). Moreover, the proposed sensor has been successfully applied for the quantitative determination of metronidazole in real drug samples. This work may provide a novel and effective analytical platform for determination of me-tronidazole in application of real pharmaceutical and biological samples analysis.