In the present work,a chemically modified electrode has been fabricated utilizing Bi2O3/ZnO nano-composite.The nanocomposite was synthesized by simple sonochemical method and characterized for its structural and morphological properties by using XRD,FESEM,EDAX,HRTEM and XPS techniques.The results clearly indicated co-existence of Bi2O3 and ZnO in the nanocomposite with chemical interaction between them.Bi2O3/ZnO nanocomposite based glassy carbon electrode(GCE)was utilized for sensitive voltammetric detection of an anti-biotic drug(balofloxacin).The modification amplified the electroactive surface area of the sensor,thus providing more sites for oxidation of analyte.Cyclic and square wave voltammograms revealed that Bi2O3/ZnO modified electrode provides excellent electrocatalytic action towards balofloxacin oxidation.The current exhibited a wide linear response in concentration range of 150-1000 nM and detection limit of 40.5 nM was attained.The modified electrode offered advantages in terms of simplicity of preparation,fair stability(RSD 1.45％),appreciable reproducibility(RSD 2.03％)and selectivity.The proposed sensor was applied for determining balofloxacin in commercial pharmaceutical formulations and blood serum samples with the mean recoveries of 99.09％and 99.5％,respectively.