Sodium alginate (NaAlg) is considered to be a potential natural polymer for biomaterial applications, because of its hydrophilic properties that is capable to increase the swelling of hydrogels and biodegradable. This study describes the synthesis of a poly (acrylamide-co-acrylic acid)-NaAlg superabsorbent hydrogels via crosslinking gamma radiation. The effect of irradiation dose (20-40 kGy) and NaAlg concentration (0. 1-0. 7%) of on swelling of hydrogels were studied. The copolymers were characterized by Fourier transform infra red spectroscopy (FTIR) and scanning electron microscopy (SEM) micrograph. The presence of the lowest (0. 1%) NaAlg concentration provokes a significant increasing the equilibrium degree solution (EDS) of hydrogel up 800 g/g, and the extent of gel fraction increases as a function irradiation dose up to about 99%. The hydrogels were also found to be sensitive to the ionic strength of medium. The FTIR spectra of hydrogels were shown crosslinking occurs between acrylamide and acrylic acid and pores structures in the hydrogel observed by using SEM.