The invention provides an organic light-emitting device and a preparation method of the organic light-emitting device. The organic light-emitting device comprises a conductive anode substrate, a hole injection layer, a hole transfer layer, a red light emitting layer, an electron transfer layer, an electron injection layer and a cathode which are sequentially stacked, wherein the electron injection layer is made of a mixed material formed by doping alkali metalhydroxide, villiaumite and lithium salt or cesium salt into an electron injection material, the electron injection material is 4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, aluminum 4-diphenol -2(2-methyl-8-hydroxyquinoline), aluminum 8-hydroxyquinoline, 3-(biphenyl-4-base)-5-(4-tertiary butylphenyl)-4-phenyl-4H-1,2,4-triazole, or 1,3,5-3(1-phenyl-1H-benzimidazole-2-base)benzene. The organic light-emitting device provided by the invention has excellent luminescence efficiency and luminescence property.