Compared to two-dimensional and one-dimensional carbon nanostructures,zero-dimensional graphene quantum dots(GQDs)with the size under 10 nm,possess strong quantum confinement and edge effects,which leads strong luminescence emission and other new physical properties [1-4].Due to these enormous merits,such as stable photoluminescence(PL),high fluorescent activity,low toxicity,excellent solubility and biocompatibility,GQDs have potential application in the fields of light-emitting diodes,bioimaging and electrochemical biosensing [5].The GQDs fluorescence has been reported to cover a broad wavelength with high quantum efficiency and shifted with the excitation wavelengths [6].However,the origin of high yield GQD fluorescence remains unclear.In this talk,we will present some new results performed by the spectroscopic and time-resolved measurements on ultra-high quantum yield GQDs.We find the wavelength dependent PL lifetime coincidence with the PL spectrum,which is very different with other semiconductor quantum dots or fluorescent dyes,such as Rhodamine6G(R6G).We demonstrate that the lifetime of GQDs can be attributed not only to molecular orbital but also to functional group of edge states.