A membrane of calmodulin (CaM) was successfully fabricated by the self-assembly. technique on a Au substrate. The electrochemical response of the membrane was investigated systematically with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods, where a redox couple of Fe(CN)(6)(3 -/4-) was employed as the probe. The results showed that a combination of CaM with Ca2+ could lead to a decrease of the reaction resistance (R-ct) The most interesting point is that the plots, which were recorded using the above two methods for the Au electrode modified with the CaM membrane (CaM/Au), showed a regular dependence on the pH of the electrolyte studied. After serial experiments, we concluded that the results we obtained could be attributed partly to the conversion process of the spatial structure of the CaM.