The effects of 0-2.5wt%Zn addition on the anti-tarnishing of 925 silver alloys were investigated. The results of phase analysising, casting analysising, microstructure observation, and anti-tarnishing performance test show that adding of 0.5wt%~1wt% Zn will improve the anti-tarnishing of 925 silver alloy obviously which is attributed to a layer of zinc oxide film formed on the surface. Adding of Zn can play a role of brightening effect and improve the casting properties.