Sputter-deposited FePt films exhibit an in-plane magnetic anisotropy when they use MgO as capped layer. The perpendicular magnetic anisotropy of FePt films are enhanced by introducing Ag capped layer instead of MgO capped layer. Although the in-plane coercivity (Hc⊥ ) of FePt films decreases slightly after introducing an Ag capper layer instead of a MgO capped layer, the perpendicular coercivity (Hc⊥ ) is increased significantly from 3169 Oe to 6726 Oe. The Auger electron spectroscopy analysis confirms that the Ag atoms diffuse from capped layer into the FePt magnetic layer and the Ag atoms mainly distribute at the grain boundary of FePt. This phenomenon results in the grain boundary energy enhancement and the grain growth inhibition and therefore increases the perpendicular coercivity and decrease the grain size of the FePt film.