Abstract: The effect of RE-Ti compound modification on the microstructure and mechanical properties of the high chromium cast iron as cast and after heat treatment was studied by scanning electron microscopy, optical microscopy and the energy dispersive spectrometer. The results show that the effect of rare earth and titanium compound modification was better than simple rare earth modification. Alarge amount dispersed TiC particles generated in substrate to refine grain. Network carbides disappeared basically, the continuity of the substrate improved obviously and the mechanical properties raised distinctly. The hardness and impact toughness reached 62 HRC and 13J·cm-2 by normalizing at 820 ℃ and tempering at 550 ℃ after modification.