Al abundances of the stars can provide important clues for exploring the chemical evolution of the globular clusters and the galaxies. In this paper, we mainly study the trends of [Al/Fe] with the stellar metallicity in stars of the thin disk, thick disk, bulge, halo of the Galaxy, and the Galactic globular clusters, such as M4 and M5. Furthermore, we investigate the correlations of [Al/Fe] with [Mg/Fe] and [Na/Fe]. For the stars in the thin disk, thick disk, and bulge of the Galaxy, their [Al/Fe] slowly decrease with the increasing [Fe/H]. However, this decreased trend does not appear in stars of M4 and M5, which implies that the contributions from Type Ia supernovae to the elemental abundances of the stars in M4 and M5 are less than those to the field stars. There are positive correlations between [Al/Fe] and [Mg/Fe] of the field stars. However, this positive correlation between [Al/Fe] and [Mg/Fe] disappears in M4 and M5 stars. Variations of [Al/Fe] have correlations with [Na/Fe] in the Galactic disk stars and stars of globular clusters, such as M4 and M5.