A novel tetraiodocadmate(Ⅱ)-selective membrane electrode consisting of tetraiodo-cadmate(Ⅱ)-rhodamin B ion pair (TICRhB) dispersed in a PVC matrix plasticized with 2-nitrophenyl octyl ether (o-NPOE) was prepared. The sensor demonstrated a near-Nernstian response for 1×10-2 to 2×10-6 mol/L cadmium (Ⅱ) at 25℃ with an anionic slope of 29.0. Itrevealed very good selectivity for Cd2+ with negligible interference from many cations and anions,and could be used in a pH range of 3 to 6.