The invention discloses a machining method for a thread rolling plate long in service life. According to the method, a carbon-nitrogen-lanthanum-yttrium ion permeating agent, a lanthanum-yttrium activated permeating agent and an oxygen ion permeating agent are utilized, a nonmetal element and a trace metal element permeate into the surface of a thread rolling plate base body, a carbon-nitrogen-lanthanum-yttrium diffusion layer and an oxygen ion diffusion layer are formed, the service life of the thread rolling plate is greatly prolonged, the treated thread rolling plate has good mechanical performance, and the precision of the thread rolling plate is not influenced from surface treatment. The permeating layer element distribution gradient of the thread rolling plate is gentle, a compound layer cannot be formed, surface stress distribution of the whole thread rolling plate is uniform, and the phenomena of thread rolling plate surface peeling, layering and the like cannot happen. The permeating agents are low in melting point and good in fluidity, the quality of the permeating layers is more uniform and stable, treatment can be conducted at the lower temperature, the diffusion efficiency of carbon-nitrogen-lanthanum-yttrium ions in the base body can be improved, and the diffusion activation energy is reduced.