The present invention belongs to the technical field of nanometer materials, and particularly relates to wavelength adjustable carbon quantum dots, a preparation method and applications thereof. According to the present invention, the one-pot method (reaction kettle) is used to synthesize, the method has characteristics of simpleness, green environmental protection and low raw material prices, the reaction temperature is 140-200 DEG C, and the great industrial production prospects are provided; according to the synthesized carbon quantum dots, the inner core has a graphitized crystal lattice structure, the outer shell is a layer of amorphous carbon and contains a lot of hydrophilic functional groups, and the carbon quantum dots has good solubility and good stability in a polar solvent, and has diameter distribution of 1.5-4 nm; the fluorescence redshift of the carbon quantum dots is generated by the change of the surface functional groups; and the wavelength adjustable carbon quantum dots adopted as the novel light-emitting material has characteristics of low production cost, low biological toxicity, high light emitting efficiency, good stability, and good application prospects in optoelectronic devices and biotechnology.