A semi-interpenetrating polymer network (semi-IPN) hydrogel based on kappa-carrageenan (KC) and poly (vinylsulfonic acid, sodium salt) (PVSA) was prepared by graft copolymerization of acrylamide (AAm) using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. FTIR spectroscopy was used for confirming the structure of the final product. It was found that the chemical composition of the Semi-IPN hydrogel is equal to the initial homopolymers; and monomer feed compositions. The swelling capacity of the hydrogel was shown to be affected by the MBA, APS, and AAm concentration as well as kappa C/PVSA weight ratio. The swelling behavior of the hydrogel was also investigated in various pHs and salt solutions. Since the highly swelling biopolymerbased hydrogel exhibits low salt-sensitivity, it may be referred to as an anti-salt superabsorbent hydrogel. The swelling kinetics of the superabsorbent hydrogels was studied as well.