A preparation process and LED application of copper nanoclusters (Cu NCs) fluorescent nanoflowers with high quantum yield by dissolving Cu4I4 into dimethyl sulfoxide (DMSO) and then adding glycerol, it self-assembles into Cu NCs s fluorescent nanoflowers. The Cu4I4 fluorescent nanoflowers prepared by the invention have outstanding optical properties, a quantum yield up to 64.5%, and can be made into a series of different luminous colors and excellent stability LED only with commercial blue phosphor, such as yellow-green, sky blue, white, wherein according to the mass ratio of 4:5 ratio mix can be prepared white light emission LED. Fluorescent Cu NCs can successfully replace traditional light conversion materials and prepare environmentally friendly LEDs.