Segmented poly(urethaneurea)s (SPUUs) were synthesized from lysine-based diisocyanate (LDI), polycaprolactone diol (PCL) and 1,4-butanediamine (BDA). The hard segment fraction was changed in order to control the mechanical properties and the degradability. The physicochemical and structural characterizations of SPUUs were carried out by infrared spectroscopy and differential scanning calorimetry (DSC), temperature dependence of dynamic viscoelasticity and small-angle X-ray scattering (SAXS). DSC showed that the glass transition temperature (Tg) of BDA-based hard segment is located at ca.373K. DSC and dynamic viscoelastic measurements revealed that Tg of soft segment increased with an increase in hard segment fraction. SAXS of SPUUs revealed the molecular aggregation states of hard and soft segments. Furthermore, the degradation behavior was investigated by exposing the polymers to a buffer solution at 310 K (pH=7.6) and activated sludge. The higher degradation rate in activated sludge compared with that in a buffer solution suggested the biodegrability of SPUUs. Finally, an electrospray deposition method was used to fabricate biodegradable SPUU nanofibers.