Abstract: The forming process and preventive measures of detrimental Fe₃C and Fe₂Ti in the microstructures of in situ processed TiC P/Fe composites have been studied. The results show that the above two harmful phases form during the solidification of Fe-Ti-C melt, and are related to the Ti content of austenite. The measures of Cu, Ni microalloying and inoculating for the melt can not only promote the synthesis of TiC particles in the melt, but also prevent effectively the harmful phases from precipitating during solidification. As a result, the properties of the composite have been improved