The invention relates to a copper selenide fluorescent quantum dot and a preparation method and application thereof. The copper selenide fluorescent quantum dot is characterized in that the quantum dot is one of Cu2Se, CuSe and Cu(2-x)Se or a combination thereof; the particle size of the quantum dot is 2-10nm, the quantum yield is 10-60%, and the half-peak width of the photoluminescence spectrum is 30-150nm. The preparation method comprises the following steps: with an aqueous solution with copper salt dissolved in as an aqueous phase and an organic solvent with a long-chain ligand dissolved in as an oil phase, stirring in an inertia protective gas, and heating in an oil bath to form a precursor solution; pouring an aqueous solution of sodium hydrogen selenide into the hot precursor solution, and heating for reaction; sampling at different time to obtain organic-phase quantum dot solutions with different emission fluorescence; precipitating the upper-layer organic-phase quantum dot solution; centrifuging and dispersing, and repeating to remove unreacted raw materials to obtain the copper selenide fluorescent quantum dot. The quantum dot does not contain heavy metal elements such as cadmium and the like to realize low toxicity, has the advantages of high quantum yield, uniform particle size, relatively narrow fluorescence emission spectrum and adjustable light color along with excitation wavelength, and can be used for preparing quantum dot solar sensitized cells and LED (light-emitting diode) devices.