Of various systems that utilize a self-propagating high-temperature synthesis, the Al-TiO2-C system is representativeof in-situ production of metal matrix composites reinforced with TiC and Al2O3. Contrary tocommon understanding, however, the following reaction 4Al + 3TiO2 + 3C→3TiC + 2Al2O3 is infeasible inthe Al-TiO2-C system with the given stoichiometric composition of 4Al + 3TiO2 + 3C. Experiments haveshown that the formation of TiC and Al2O3 is feasible only in an Al-TiO2-C system that contains a certainamount of excess Al. In this study, the mechanism of the reactions in the Al-TiO2-C system was elucidated inorder to explain why excess Al is needed to promote the formation of TiC and Al2O3. We also estimatedthe amount of excess Al that is necessary to promote the complete transformation of the Al-TiO2-C powdersto TiC and Al2O3.