Abstract: The mechanism of in situ TiC/Al composite synthesis with XD method was studied by using DTA, X ray diffraction, TEM and optical microscopy. The results show that Al₃Ti phase forms firstly in aluminium matrix and then TiC phase is synthesized through the reaction between Al₃Ti phase and C powder. It is thought that Al acts as a catalyst during TiC formation, lowering activation energy and favoring the reaction.