In as-cast structure of AISI M2 steel, the predominant type of eutectic carbides is M₂C, the morphology of which has crucial influence on the distribution and dimension of carbides in final products. In the present work, the morphology and properties of M₂C carbides formed at different cooling conditions have been investigated by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), X-ray diffraction (XRD) and differential thermal analysis (DTA). With increasing cooling rates, the morphology of M₂C transforms from the lamellar type to the rod-like one, and the two carbides show different growing characteristics during solidification. Compared with the lamellar carbides, rod-like M₂C is less stable and decomposes faster at high temperatures, accelerating the separation and spheroidization of carbides, even after hot deformation. It is concluded that the formation of rod-like M₂C in cast ingots promotes homogeneous distribution and refinement of carbides in the final products, favoring the improvement of mechanical properties of high speed steels.