A series of lithium and sodium salts of sulfonated polyethylene oxide (PEG) polyurethane ionomers in different levels of ionization were prepared. It has been found that this material is a new type of ionic conductive polymer, characterized by a single-ion transport mechanism and good mechanical properties. The ionization level significantly influences the ionic conductivity of the samples. When the mole ratio of the metal ion and ether oxygen atom is about 0.05, the ionomers exhibit maximum cationic conductivity. An optimal cationic conductivity of 1.0 X 10(-5) S/cm is obtained at about 70 degrees C without any addition of organic plasticizer. The conductivity increases apparently when propylene carbonate and low MW PEO are added to the polyurethane ionomer.