Abstract: :An ampholytic hydrogel， P(ε-acrylic-L-lysine-co-acrylamide) （P(εACRLLY-co-AM)）， containing free amino acid side chains is prepared. The hydrogel exhibits apparent ampholytic behavior and has a broad isoelectric point (pH=4~10) through researching the change of swelling degree of hydrogel with pH values and salts concentration. At the same pH, a series of hydrogels have the similar swelling kinetics behavior. However, the hydrogel has the different swelling processes in varied pH solution resulting from the different ionized states of amino acid. The swelling deswelling kinetics behavior of hydrogel shows a large hysteresis appeared in deswelling process in different pH solution cycles. The molecules of hydrogel has intra or inter hydrogen bonding in lower pH values by investigating the change of swelling degree of hydrogel in variation pH with urea concentration.