An optimal new PVC membrane sensor for Cd2+ ions based on TRLAR3-(2',4'dihydroxyphenylazo-1')-1,2,4 triazol as the active substance was prepared. Its basic analytical parameters such as slope characteristics; detection limit; lifetime; response time; selectivity for zinc, nickel, cobalt calcium, copper, barium, magnesium, manganese, potassium and sodium ions, as well as the dependence of the electrode potential on pH were established. The proposed membrane sensor can be used in flow injection potentiometric analysis of cadmium ions.