A new electroactive polynuclear inorganic compound of a rare earth metal hexacyanoferrate, samarium hexacyanoferrate (SmHCF), was prepared by electrochemical deposition on the surface of a glassy carbon electrode with a potential cycling procedure. The cyclic voltammogram of SmHCF exhibits a pair of well-defined redox peaks with a formal potential of 191 mV (vs. SCE) at a scan rate of 100 mV/s in 0.2 M NaCl solution and the redox peak currents increase linearly with the scan rate up to 100 mV/s. The effects of the concentration of supporting electrolyte on the electrochemical characteristics of SmHCF and the transport behavior of K+, Na+ and Li+ counter ions through the ion channels of SmHCF were studied by voltammetry. The different electrochemical behavior of SmHCF in various cation-containing supporting electrolytes was investigated by cyclic voltammetry and scanning electron microscopy. The SmHCF was also characterized by FTIR techniques.