-Carrageenan comes from a family of linear water-soluble polysaccharides extracted from different species of marine red algae and is composed of an alternating disaccharide repeating unit of α-(1-3)-D-galactose-4-sulphate and β-(1-4) 3,6-anydro-D-galactose. The 1C4 conformation of the 3,6-anhydro-D-galactose units allows a helicoidal secondary structure, which is essential for -carrageenan to gel in water. The gelation of -carrageenan in aqueous solution is generally accepted as a two-step model involving a transition of coils to helices followed by aggregation of helices. A -carrageenan solution changes its state from a liquid to a solid (= gel) in the vicinity of a critical value of a gelling parameter (e.g. temperature or concentration) which is referred to as the gel point. For -carrageenan gels, a three-dimensional network is composed of helical aggregates as the junctions, and flexible chains connecting the junction zones. However, rheological studies of -carrageenan in aqueous solution did not explore the region of sol-gel transition and the detail of junction structure so far. Our studies verified that κ-carrageenan hydrogels were formed by the formation of fibrils, and the fibrillar diameter increased with increasing -carrageenan concentration. The formation and melting of -carrageenan gels were thermally reversible and extremely sensitive to -carrageenan concentration. In comparison with the crossover of G’ and G’’, the extrapolation method based on multiwave oscillation and Winter-Chambon criterion were able to give more accurate critical gel temperature Tc. At the gel point, the critical relaxation exponent n was almost constant and independent of temperature and -carrageenan concentration, whereas the critical gel strength Sg increased with increasing critical gel concentration cg. A constant gel strength Sg/cg was obtained by normalizing Sg with cg to eliminate the effect of temperature or cg, showing a unique character of κ-carrageenan in aqueous solution during gelation. The molecular structure of the junctions at the gel point was analyzed using the modified Eldridge-Ferry model shown in Figure 1, which supported the similarity of the fractal structure in the κ-carrageenan hydrogels κ-carrageenan, scaling law, rheology.