▎ 摘　　要

NOVELTY - Method of preparing magnetic graphene quantum dot involves subjecting ferrous ascorbate aqueous solution to hydrothermal reaction. USE - Method of preparing magnetic graphene quantum dot that is used for preparing enhanced imaging contrast agent and in vitro diagnostic probe, where enhanced imaging contrast agent is nuclear magnetic resonance-fluorescence double-mode enhanced imaging contrast agent, and in vitro diagnostic probe is nuclear magnetic resonance relaxation-fluorescence double-mode in vitro diagnosis probe (all claimed). ADVANTAGE - The method rapidly provides magnetic graphene quantum dot having shortened imaging time, improved imaging contrast, improved accuracy of imaging diagnosis, and improved accuracy of in vitro diagnostic techniques, in convenient manner. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: 1. Magnetic graphene quantum dot, which is prepared by the method; and 2. use of magnetic graphene quantum dot in preparation of enhanced imaging contrast agent.