The invention discloses a light-emitting diode epitaxial wafer and a manufacturing method thereof, and belongs to the technical field of a semiconductor. An epitaxial wafer comprises a sapphire substrate, a buffer layer, a nucleating layer, an un-doped GaN layer, an N-type layer, an active layer and a P-type layer, wherein the buffer layer, the nucleating layer, the un-doped GaN layer, the N-type layer, the active layer and the P-type layer are stacked up on the sapphire substrate in sequence. The epitaxial wafer also comprises an improvement layer. The improvement layer comprises SiN layers and GaN layers, which are stacked up alternately. The improvement layer is arranged between the un-doped GaN layer and the N-type layer, or between the N-type layer and the active layer. The improvement layer is arranged between the un-doped GaN layer and the N-type layer, or between the N-type layer and the active layer, and the improvement layer comprises the SiN layers and the GaN layers, which are stacked up alternately, wherein the SiN layers and the GaN layers, which are stacked up alternately, are in a superlattice structure, so that stress can be released effectively, thereby reducing defects of the active layer, improving crystal quality, improving performance and reliability of the epitaxial wafer, and improving backward voltage of a chip formed by the epitaxial wafer.