Electrocatalytic oxidation of thiosulfate at the 2,7-BFEFMCPE occurs at a potential about 460 mV less positive than that unmodified carbon paste electrode.The diffusion coefficient(=5.6 × 10-5 cm2 s-1),the kinetic parameters such as electron transfer coefficient,(=0.5)and kh(=1.21 × 10-3 cm s-1)of thiosulfate oxidation at the surface of,2,7-BFEFMCPE were determined.The electrocatalytic oxidation peak current of thiosulfate showed two linear dynamic ranges(0.00(0-0.009 mmol/L and 0.009-0.900 mmol/L)and a detection limit of 0.00015 mmol/L.This method was also examined as a new electrochemical sensor for the determination of thiosulfate in real sample.