Abstract: The kinetic mechanism of XD reaction in Al-TiO₂-C system was studied in this paper. Result shows that a strong exothermic reaction results in the formation of a high temperature metallurgical micro-region in the sample, which is favorable to synthesis of reinforcing particles TiC_p / (Al₂O₃)_P and in matrix alloying. Synthetic reactions take place as different kinetic mechanisms in different periods. There exists a crack of the reactants during the quick reaction period,the cracking was caused by the steep temperature gradient and great thermal stress inside the reactants. The cracking of reactants makes the reaction speed very fast and synthesized particles (Al₂O₃)_P and TiC_P very fine.