Abstract: Graphene quantum dots (GQDs) have attracted extensive attention due to their excellent optical properties and biocompatibility. By modification, the conjugated system of surface structure can be changed, and the separation rate of electron hole pair, optical band gap and luminescence characteristics can be adjusted. Furthermore, their applications in biological imaging, chemical sensing and photocatalysis will be broadened. The preparation methods of GQDs including top-down and bottom-up methods are briefly introduced. The doping methods and the effects of different doping elements on GQDs, grafting modification based on surface functional groups and construction of composite materials consisted of GQDs and other semiconductors are reviewed in details. The applications of graphene quantum dots composites in biological imaging, fluorescence sensing, photocatalysis and other related fields are summarized. Finally, the future research directions of graphene quantum dots are prospected from the aspects of preparation methods, mechanism exploration, performance regulation and application effects.