A series of glutathione-responsive biodegradable poly(urea-urethane)s were synthesized from poly(ethylene glycol) as the soft segment and 1,6-hexamelthylene diisocyanate incorporating cystine-based chain extender as the hard segment. Structure and thermal properties of the poly(urea-urethane)s were characterized with attenuated total reflectance Fourier transform infrared, (1)H NMR, gel permeation chromatography, differential scanning calorimeter and thermogravimetric analyses. In vitro degradation test was carried out under physiological conditions in the presence of glutathione and the degradability of poly(urea-urethane)s were evaluated by the decrease in their molecular weight (M w), on which the degradation rate constants were calculated and kinetic equations were established. PU[Cys] had the highest degradation rate and it remained only 30% of the original M w in eight days. All the poly(urea-urethane)s were testified with noncytotoxicity and good biocompatibility.