A method for preparing a light-emitting diode having a vertical structure by stripping a GaN base epitaxial layer and a sapphire substrate by a wet process, the method including: a) preparing a graphical growth substrate; b) growing a GaN base light-emitting diode epitaxial layer on the graphical growth substrate, the GaN base light-emitting diode epitaxial layer from the bottom to the top successively including a N-type GaN layer and a P-type GaN layer; c) successively forming a transparent and electrically conductive film, an omni-directional reflection layer, an electrically conductive reflection layer, and a passive metal protection layer from the bottom to the top on the GaN base light-emitting diode epitaxial layer; and d) removing the first layer of stable material with a high melting point of the growth substrate by dry etching, exposing the N-type GaN layer, and preparing an N electrode on the N-type GaN layer.