Graphene quantum dot is one of the most important derivants of graphene. With the quantum size effect, graphene quantum dots show a distinct semiconductive nature, compared with intrinsic graphene. Graphene quantum dots have a high application value in fluorescent anti-counterfeiting materials, biological imaging, tumor diagnosis and treatment, and photo/electrocatalysis due to their superior photoluminescence properties, high stability, low biotoxicity, modulated interface structure. This review represented the photoluminescence properties of graphene quantum dots. The bandgap structure of graphene quantum dots, which is related to the important basic physical properties of the material in various applications was summarized. This review can provide a reference for the future studies on the photoluminescence performance modulation and mechanism of graphene quantum dots.