Abstract: Water-soluble GO-Gd@C82 nanohybrids exhibited high relaxivities and could be explored as potential magnetic resonance imaging (MRI) contrast agents. To better understand the relaxation mechanism in the novel carbon nanohybrids, in this presentation, after the layers of in-depth analysis and exploration, we proposed that the structure and the physicochemical properties of carbon nanohybrids contributed a lot to the enhanced relaxivity. The better electron transfer from Gd@C82 to the GO nanosheet, the appropriate electric conductivity and the size of GO, the increased number of H proton exchange sites and the enough concentration of Gd3+ should be in the optimal equilibrium for higher relaxivity of GO-Gd@C82. This result is important for constructing and optimizing the novel architecture of nanoscale with higher relaxivity.