The electrochemistry behaviors of different concentration of Fe(CN)₆^3-/Fe(CN)₆^4- at the gold electrode modified with dodecylthiol self-assembled monolayer were investigated with electrochemical impedance spectroscopy and cyclic voltammetry technology. It is determined that the apparent heterogeneous rate constant k_s is in the order o f 10^-8m·s^-1. It is found the apparent transfer coefficients α+β≠1. The electron transfer between the gold surface and the redox species separated by the monolayer assembly may complete by electron tunneling. The electron tunneling constant is estimated in the range of (0.83～1.11)/CH₂ which is consistent with literatures.