The invention discloses a preparation method of an anti-carburizing electrothermal alloy, and relates to the iron chromium aluminum alloy processing and manufacturing field; the preparation method includes five technological processes of alloy smelting, steel wire rod preparation, heat treatment, alkali boiling and pickling, and drawing; in the preparation method, a medium-frequency vacuum induction furnace is selected as a melting device, moreover, through strict control of a tapping temperature, a furnace material undergoes a full reaction in the furnace, a smelting effect is good, and a prepared electrothermal alloy steel ingot has good quality; in a forging process, through control of a die forging temperature, the surface quality and the core part quality of a fogged steel wire rod are both relatively good, the steel wire rod after rolling is subjected to alkali boiling and pickling processes, an oxidation film on the surface of an electrothermal alloy wire is basically cleaned, impurity residues are few, and the anti-carburizing electrothermal alloy wire produced by the preparation method has strong anti-carburizing ability, can be widely used in heating elements in a carburizing furnace, and is long in service life, good in weldability, intact in welding surface and worthy of promotion.