The invention discloses a preparation method of high-activity functionalized graphene capable of adsorbing fungaltoxin. Graphene oxide dispersion liquid of a single-layer or multi-layer structure and surfactant are mixed, then, a mixture is subjected to forth ultrasonic processing and is stirred for 24 to 48h at room temperature to obtain even mixed liquor, and the mixed liquor is stirred at the temperature of 70 to 95DEG C for 6 to 10h to obtain the functionalized graphene. The graphene oxide is taken as a raw material, amphipathy surfactant is used as modifier, the graphene is subjected to covalence functional modification through ion exchange and amidation reaction, the functionalized graphene with good soluble dispersion capacity is obtained, and the adsorption performance of the functionalized graphene is improved. The functionalized graphene has an outstanding adsorption effect on the fungaltoxin, and has high practical value and good application prospect.