In this work, a high-sensitive electrochemical sensor of Norfloxacin (NFX) has been developed using a composite electrode of MWCNT-CPE/pRGO-ANSA/Au. MWCNT-CPE is the multi-walled carbon nanotubes (MWCNT) - carbon paste electrode (CPE). pRGO-ANSA means the partially reduced graphene oxide (pRGO) - 6-aminonaphthalene-2-sulphonic acid (ANSA) hybrid nanomaterials. Au represents gold nanoparticles. The electrochemical sensing of NFX was investigated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and differential pulse voltammetry (DPV). Experimental results show that the combination of MWCNT-CPE/pRGO-ANSA/Au offers high electrical conductivity, large surface area and excellent electrocatalytic activity, being beneficial for electrochemical sensing performance. The calibration curves of NFX exhibit linear response in the NFX concentration range of 0.03-1.0 and 1.0-50.0 mu M, with the limit of detection (LOD) of 0.016 mu M (S/N = 3). The fabricated sensors were successfully applied for detecting the presence of NFX in pharmaceutical formulations and rat plasma samples. The measured results were comparable with those obtained using ultrahigh performance liquid chromatography (UHPLC), indicating its high potential for applications in pharmaceutical analysis and clinical therapeutic drug monitoring. (C) 2017 Elsevier B.V. All rights reserved.