As far as the longitudinal relaxivity (r₁) is concerned, gadolinium ions (Gd³⁺)-based MRI contrast agents modified by traditional carriers do not appear to be far superior to the clinically used Magnevist. In this study, a type of MRI contrast agent (Gd³⁺@CGO) possessing a significantly high r₁ value was easily prepared using a carboxyl-functionalized graphene oxide (CGO) as a nanocarrier to directly interact with GdCl₃·6H₂O. With 2.8 wt% of Gd³⁺ loaded on CGO, the prepared Gd³⁺@CGO shows good dispersibility in water and possesses r₁ of 63.8 mM⁻¹ S⁻¹, which is 14 times higher than that of Magnevist. It is exciting to note that Gd³⁺ anchored on CGO remains stable at least for one year, probably relying on the electrostatic adsorption and physical encapsulation effect of CGO towards Gd³⁺.