Abstract: For the disadvantages of traditional mold flux of peritectic steel, this paper proposed a novel type of mold flux, which combined both heat transfer and lubrication effects, providing a new solution for the stable highefficiency production of peritectic steel billet. Through the proper decrease of basicity and viscosity of previous mold flux for peritectic steel，introduction of LiO₂ and oxides of transition metallic elements（Fe₂O₃，MnO），as well as the content reduction of fluorine, the applicability and stability of the mold flux for the casting of peritectic steel billet at high casting speed were improved. In view of associrelation and compatibility of series flux properties, as well as service conditions, the qualified ratio of defect-inspection for the peritectic steel billet was highly improved from less than 35 % to more than 93 %，and a continuous high-efficiency and high-quality production way of peritectic steel billet was achieved with the appropriate employment of the novel mold flux for peritectic steel.

Key words: peritectic steel, mold flux, billet, surface quality, high casting speed