A zwitterionic polymer-poly-3-dimethyl(methacryloyloxyethyl)ammonium propane sulfonate (PDMAPS)-was synthesized and its complexation behaviors with polyanion: poly-2-acrylamido-2-methyl propane sulfonic acid (PAMPS); and polycation: poly-3-acryloylamino propyl trimethyl ammonium chloride (PDMAPAA-Q); or: x,y-ionene bromides (x = 3,6; y = 3,4) have been studied. One of the characteristic features of these complexes is that they are soluble, in spite of the abolishment of positive or negative charge of PDMAPS after the complexation and is able to exhibit UCST depending on the concentration and the mixing molar ratio. It was found that PDMAPS-PAMPS complex dramatically increases the viscosity to give a network structure through electrostatic interaction extensively decreasing the UCST, while the PDMAPS-polycation complex first decreases, but then increases the UCST without forming the network. The mechanism of different behaviors of these complexes has been discussed.