For the fabrication of magnetically supramolecular hydrogels, the aqueous colloidal dispersion of magnetic iron oxide nanoparticles was first stabilized by an amphiphilic poly (epsilon-caprolactone)-poly (ethylene glycol) (PEG-PCL) block copolymer and then mixed with an aqueous solution of a cyclic oligosaccharide. Due to the host-guest interaction between the used block copolymer and the cyclic oligosaccharide in the aqueous mixed system, such a fabrication process could result in the formation of a novel hydrogel nanocomposite with superparamagnetic property, as confirmed by the analyses from rheology and X-ray diffraction as well as magnetization curve measurements. For the resultant magnetically supramolecular hydrogel, its formation kinetics and mechanical strength could be modulated by the amount of the used PEG-PCL block copolymer, the cyclic oligosaccharide, or the incorporated iron oxide nanoparticles.