The invention discloses an AlGaN-based deep ultraviolet LED epitaxial wafer and a preparation method thereof. The AlGaN-based deep-ultraviolet LED epitaxial wafer comprises a silicon carbide substrate, an Ag layer deposited on the silicon carbide substrate, an AlN buffer layer grown on the Ag layer, an AlGaN buffer layer grown on the AlN buffer layer, a non-doped AlGaN layer grown on the AlGaN buffer layer, an n-type doped AlGaN layer grown on the non-doped AlGaN layer, an AlGaN multi-quantum well layer grown on the n-type doped AlGaN layer, an electron blocking layer grown on the AlGaN multi-quantum well layer, and a p-type doped GaN film grown on the electron blocking layer. According to the invention, a stripping process is not needed, the external quantum efficiency is greatly improved, dislocation formation can be reduced, the radiation recombination efficiency of carriers is improved, the deep ultraviolet LED with high thermal conductivity, high electric conductivity and high light-emitting performance can be obtained, the current distribution of the deep ultraviolet LED is more uniform, the light extraction efficiency is improved, and the heat dissipation capability is good; and the preparation process is simple and has repeatability.