|| Recently, thermo-responsive polymer gels have been studied in various research fields such as drug delivery system. One of represetative thermo-responsive polymer gels is poly(N-isopropylacrylamide) gel (PNIPAAm) that has a rapid and reversible volume phase transition. However, PNIPAAm is not biodegradable, resulting in limitation of its use in medical fields. Novel thermo-responsive polymer gel was prepared by closslinking of isopropylamine modified poly(succinimide) (IPA-PSI) (Poly[α,β -(DL-aspartate isopropyl amide)-co-(succinimide)]) with hexamethylenediamine. Because of peptide bonds in backbone, therefore, it is expected to possess biodegradability and biocompatibility. These gels changed their volume in response to change of environment such as temperature, pH and concentration of salt in water. Crosslinkage density and substitution degree of IPA-PSI affected volume phase transition bahavior of the gel.