This paper describes the effect of 5-nm thick platinum (N), aluminum (Al) and silicon oxide (SiOx) capping layers on the static and dynamic magnetic properties of 400-nm thick polycrystalline YIG films deposited on a N buffer layer. Both static and dynamic magnetic properties of N capped YIG film are totally different among all YIG films. Namely, the squareness of the magnetization curve for N capped YIG film increases, indicating that N capped YIG film is magnetically softer than other YIG films. Interestingly, the effective Gilbert damping parameter of N capped YIG films is about four times as large as those of other YIG films, and its value is approximately 9.52 x 10(-4). However, the value of Gilbert damping is 2.55 x 10(-4), 3.46 x 10(-4) and 3.85 x 10(-4) respectively for no capping, SiOx capping and Al capping samples respectively. This huge change in Gilbert damping parameter is mainly originating from the spin pumping effect, which arises at the interface of a material having strong spin orbit interaction such as N. Moreover, the enourmous increase in the value of effective anisotropic field and decrese in effective saturation magnetization indicates interface anisotropy is induced in N capped sample. These results suggest that the static and dynamic magnetic properties of YIG film can be controlled by selecting an appropriate capping layer.