The invention discloses a gallium nitride-based light emitting diode epitaxial wafer and a preparation method thereof, and belongs to the technical field of semiconductors. The gallium nitride-based light emitting diode epitaxial wafer comprises a substrate, a buffer layer, an N-type semiconductor layer, an active layer, and a P-type semiconductor layer, and the buffer layer, the N-type semiconductor layer, the active layer, and the P-type semiconductor layer are sequentially stacked on the substrate; the active layer comprises a plurality of quantum wells and a plurality of quantum barriers,and the plurality of quantum wells and the plurality of quantum barriers are alternately stacked; and at least one boron hydride layer is inserted into the quantum barrier. According to the epitaxialwafer and the preparation method in the invention, at least one boron hydride layer is inserted into the quantum barrier, and the thermal conductivity of the boron hydride layer is good, so the heat generated by combined luminescence of electrons and holes in the active layer can be conducted out in time to prevent the junction temperature of the active layer from rising, thereby facilitating theimprovement of combined luminous efficiency of the electrons and holes, and further improving the luminous efficiency of the LED, and the gallium nitride-based light emitting diode epitaxial wafer isparticularly suitable for LEDs at a high current density.