A mixed-valence cluster of cobalt(II)hexacyanoferrate possesses an electron transfer property and is suitable for the development of an effective hydrogen peroxide detection scheme. The characteristics of cobalt(II)hexacyanoferrate have been studied using both elemental analysis and infrared spectra, confirming the structure is Comath image[FeII(CN)6]. The cobalt(II)hexacyanoferrate-modified electrode exhibits a rapid response (t95% - 6.5 s) to the injection of 5.0 × 10−5 M hydrogen peroxide. The linearity of the response is up to 1.1 × 10−3 M (correlation coefficients is 0.999). The sensitivity of this modified electrode is 11.8 μA/mM-mm2. The detection limit of cobalt(II)hexacyanoferrate-modified electrode to hydrogen peroxide is 6.25 × 10−8 M. The current chemical sensor modified with Comath image[FeII(CN)6] has better sensitivity than previous ones. The modified glassy carbon electrode shows no interference from ascorbic acid, uric acid, acetaminophen, 1,4-dihydroxyquinone, dopamine at the 2.0 × 10−4 M level and polyamines at 5.0 × 10−5 M level.