The invention discloses a preparation method of an iron-based nucleating agent for high speed steel, and relates to an iron-base alloy manufactured by a smelting process. The iron-based nucleating agent is a thin-band-shaped nucleating agent of NbC-VC-Yb2C3/Fe nano two-dimensional in-situ synthesized iron-based composite for the high speed steel. The iron-based nucleating agent is prepared by an in-situ synthesis process and a metal rapid solidification technology, and the defects that a nucleating agent prepared in the prior art is poor in wettability, the nucleating effect is not uniform, the sizes of enhanced particles are larger, and the nucleating agent does not have the function of eliminating or weakening deleterious effects of a sulfur element in steel are overcome.