The gallium hexacyanoferrate (GaHCF) was synthesized chemically and characterized by FTIR technique. Its electrochemical behavior was carefully investigated by fabricating a GaHCF modified carbon paste electrode in various supporting electrolyte. The experimental results showed that in KNO 3 , K 2 SO 4 , KCl and other supporting electrolyte, GaHCF yielded one pair of ill-defined redox waves with a formal potential of 0.9V (versus SCE). In 0.050molL −1 phosphate buffer solution (PBS, pH 6.8), however, GaHCF yielded one pair of well-defined redox peaks with a formal potential of 0.222V. Furthermore, this modified electrode exhibited a high electrocatalytic activity toward the reduction of H 2 O 2 in pH 6.8 PBS, with over-potential dramatically lower than that of on the bare carbon paste electrode. Amperometry was used for the determination of H 2 O 2 , under the optimal conditions, a linear dependence of the catalytic current versus H 2 O 2 concentration was obtained in the range of 4.9×10 −6 to 4.0×10 −4 molL −1 with a detection limit of 1×10 −6 molL −1 when the signal-to-noise ratio was 3, and a sensitivity of 27.9μAmM −1 (correlation coefficient of 0.997). Chronoamperometry was used to conveniently determine the diffusion coefficient of H 2 O 2 in the solution.