The invention relates to the technical field of photoelectricity, and discloses a light-emitting
diode epitaxial
wafer and a preparation method thereof, and an LED, the light-emitting
diode epitaxial
wafer comprises a substrate, and the substrate is sequentially provided with a buffer layer, a non-doped GaN layer, an N-type GaN layer, a stress release layer, a multi-
quantum well layer, an
electron blocking layer, and a P-type GaN layer; the multi-
quantum well layer comprises a high-barrier multi-
quantum well layer, a middle-barrier multi-
quantum well layer, a low-barrier multi-
quantum well layer and a low-barrier end multi-
quantum well layer which are stacked in sequence. According to the light-emitting
diode epitaxial
wafer provided by the invention, the hole injection efficiency of the P-type
semiconductor material can be improved, the phenomenon of insufficient hole concentration in the multi-quantum well layer is improved, and the matching degree of
electron hole concentration in the multi-quantum well layer is improved, so that the
radiation recombination efficiency in the multi-quantum well layer is improved, and the brightness and the lighting effect of an LED device are finally improved.