The microstructures of the siliconized specimens of Ti-48Al alloy were analyzed by SEM equipped with XEDS.The specimens were pack siliconized with the two different cementations, 15%Si+85% Al2O3 and 15%Si+85%ZrO2. The results show that a composite siliconized layer is formed on the surface of the TiAl alloy. The outer layer is the continuous Al2O3 where a lot of Si particles adhered; the inner layer is most of Ti5Si3 with amount of Al2O3 particles dispersed in. It was deduced that the Al2O3 in the cementation layer is formed by the Al atoms in the TiAl substrate react with the residual O in the face and in the TiAl substrate.