The co-producing monomethylolamine which provides both the source and the carbon source is used as a precursor, and the microwave is used as a heating means to achieve the stirring at the molecular level, and the uniform small-sized Gd3 + doped carbon quantum is obtained at a low temperature and in a short time. The purpose of the point (Gd3 + /CQDs-MH). When the current body is hydrothermally reacted at 250 °C for 45 min, the obtained Gd3 + /CQDs-MH exhibits high quantum yield and extremely strong magnetic resonance performance, avoiding the luminescence of carbon quantum dots by the traditional heating method. The ability and relaxation performance are extremely difficult to increase at the same time. Under this condition, carbon quantum dots with a size of about 1.0 nm were synthesized with a fluorescence quantum yield of 11.0%, a doping mass fraction of Gd3 + of 16.9%, and a longitudinal relaxation performance of up to 4 545.3 mmol. -1· L·s -1 ([Gd3 +]= 0.01 mmol· L -1 ). Moreover, the carbon quantum dots have no obvious toxicity to HeLa cells, and are expected to be used as magnetic resonance-fluorescence bimodal probes with high relaxation performance and high luminescence properties.