Electrochemical impedance spectroscopy (EIS) has been used to study the graphite composite electrode/electrolyte interface in a newly designed three-electrode button-type cell. In order to follow the formation of the passivation film on graphite, several spectra have been plotted during the first reduction of the electrochemical system. Typical impedance spectra exhibit a high-frequency (HF) impedance loop, which does not evolve much over the scanned potential range. A middle-frequency (MF) loop appears as the cathodic polarization of the carbon electrode increases, whose characteristics are potential dependent. In the lower frequency (LF) region, a near vertical straight line is observed. The attributions of each frequency region are discussed in the present paper.