Gelatin-based　hydrogels　have　multiple　advantages　because　of　their　biocompatibility,　biodegradability,　and　nontoxic　properties.　The　feasibility　of　using　gelatin-based　hydrogels　could　be　greatly　improved　if　they　could　overcome　the　weak　mechanical　property　for　application.　Here,　strong　fish　gelatin　hydrogels　were　prepared　by　introducing　kappa-carrageenan　to　gelatin　solution　to　form　structure　preliminarily　enhanced　gelatin　hydrogel,　followed　by　immersing　in　10　wt%　concentration　of　K2SO4　solution.　The　modified　hydrogels　have　an　extraordinary　hardness　(21.22　N)　and　storage　modulus　(＞10(4)　Pa)　when　carrageenan　amount　was　0.8　wt%,　superior　to　those　of　unmodified　gelatin　hydrogel.　The　effects　of　carrageenan　concentrations　on　thermal　stability,　water　distribution　and　microstructures　of　hydrogels　were　systematically　evaluated,　and　the　possible　strengthening　mechanism　was　also　discussed.　This　article　provided　a　simple　method　for　the　preparation　of　gelatin　hydrogels　with　strong　structure　and　the　modified　hydrogels　can　be　used　in　foods,　materials　and　other　fields.