The invention discloses a machining method for improving an aluminum pressure casting and precision forging die. According to the method, a carbon, nitrogen, lanthanum and yttrium permeability agent,a lanthanum and yttrium excitation permeability agent and an oxygen ion permeability agent are used, a non-metallic element and a trace metal element permeate the surface of a die base body, a carbon,nitrogen, lanthanum and yttrium diffusion layer and an oxygen ion diffusion layer are formed, the service life of the die is greatly prolonged, the treated die has the good mechanical property, and the die accuracy is not influenced by surface treatment. A permeable layer element distribution gradient of the die is gentle, a compound layer is not formed, the overall die surface stress distribution is even, and die surface peeling, layering and the like are avoided. According to the machining method, the permeability agent melting points are low, mobility is good, the permeable layer quality is more even and stable, treatment can be carried out at lower temperature, the diffusion efficiency of carbon, nitrogen, lanthanum and yttrium ions in the base body can be improved, and the activationenergy of diffusion is reduced.