Abstract: Water soluble polyurethane ureas(PUU) were synthesized by prepolymerization of poly oxidepropene glycol and toluene diisocyanate, and by chain extending with diethylenetriamine and then neutralized by anhydrous acetic acid. Viscositie s of PUU solutions at different concentrations were measured by Ubbelohde capillary tube viscometer, and the PUU molecular sizes were also calculated by Huggins, Kr aemer equation and Fox, Flory equivalent pellet theory. The results demonstrate that the dimensions of the water solube PUU chain increase with the molecular w eight in water; and the decreasing of the PUU E(containing the polyether diol w i th n=1 911) chain size by addition of sodium acetate reveals that th e chain conformation is changed from the stretch to winding form, and the viscos ity is declined because of decreasing effective volume fraction. The results als o indicate that the PUU chain size in water is determined by the steric hindranc e, and the range of the PUU sizes is close to that of the solute molecules in t rue solution(10 -10 m~10 -9 m). The rheological properties of the PUU at different concentrations reveal that the water solube PUU should belong to New tonia fluid, and the apparent viscosity of PUU is not changed with shear rate, a nd the viscosities of the dilute solution(1%) of PUU are close and similar to th e results of Ubbelohde viscosimeter, and independent on the molecular weight. Wi th the concentration increasing, the PUU viscosity increases, while the viscosit y of the thick PUU decreases by increasing the molecular weight. The Newtonia fl ow behaviour of PUU solutions elucidates that the conformation of the PUU chain is stable in water, and not influenced by shear stress.