Abstract: Seven tetra-alkyl ammonium salts have been tested as the electro-active material for the PVC-based membrane tetrachloroferrate(Ⅲ) ion-selective electrodes. The electrode based on the tetrachloroferrate (Ⅲ) salt of trioctylhexadecylammonium as the electroactive material was considered to be the best. At 25℃, the electrode shows Nernstian response for tetrachloroferrate (Ⅲ) ion over the concentration range from l×10^-2M to 7×10^-6Miron (Ⅲ) with a slope of 60mV/pFe.The detection limit is down to 2.5×10^-6M iron (Ⅲ) in the 5M NaCl-0.05 MHC1 solution. Sn⁴⁺, Hg²⁺, Cd²⁺ and Zn²⁺ in a more or less extent interfere. The possibility of determination of iron (Ⅲ) in solutions of high Cl^- concentration has been discussed.