The effect of pack aluminizing fillers (Al2O3, Y2O3) on the aluminide coatings are studied by changing the traditional pack aluminizing. The phases and the surface morphologies of aluminide coatings before and after oxidation are examined by XRD and SEM. The results show that the pack aluminizing fillers take part in the aluminizing process, which does not only keep the Al power from sintering, but also affect the phases in the aluminide coatings. The aluminide coatings with the pack aluminizing fillers (Al2O3) are mainly composed of Al3Ti + AlTi + AlTi3 phase, but mainly of AlTi3 phase when the pack aluminizing fillers contain Y2O3, which conflicts with the traditional mechanism of pack aluminizing. The pack aluminizing fillers also have much effect on the surface morphologies of aluminide coatings before and after oxidation and the style of Al2O3 crystal lattice.