Ti2AlC/Al2O3 nanocomposites were synthesized by high energy milling with Ti, C, Al and TiO2 as initial materials. The formation and evolution of phases in high energy milling and following heat treatment were investigated by X-ray diffractometer (XRD). The results show that the raw materials of Ti, C, Al and TiO2 were pulverized to ultrafine particles, and some of them transformed to amorphous phase. When the as-milled powders were heat treated in vacuum atmosphere, TiC was firstly produced and released large amount of reactive heat, which resulted in the reaction between Ti and Al to produce intermediate phases of the TixAly (TiAl3, TiAl, and Ti3Al) intermetallics. The reaction between Al and TiO2 produced Al2O3 phase. The TixAly intermetallics and the residual Ti and Al transformed to TiAl equilibrium phase. Finally, the TiAl intermetallics and the TiC reacted to yield Ti2AlC, which produced Ti2AlC/Al2O3 nanocomposite together with the former in-situ formed Al2O3.