The invention provides a preparation method of an iron-based inoculant for bearing steel and relates to the manufacturing of an iron-based alloy through a melting method. According to the preparationmethod, the Fe-Nb-Cr-C amorphous nanocrystalline iron-based inoculant which is used for the bearing steel as well as contains amorphous and nanometer reinforced particles of NbC, Cr7C3 and CrC is prepared through an in-situ synthesis method and a quick quenching technology. By the adoption of the iron-based inoculant, the defects that in the prior art, no special inoculant used for the bearing steel exists, no inoculant with the function of directionally increasing the quantity of M7C3-type carbides in the bearing steel exists, no inoculant with a very good reinforced phase and the very high bearing steel wettability exists, and no method for reducing the loss of the reinforced phase in the inoculant at high temperature exists can be overcome.