Abstract: Medium performance variation infection for high electromegnetic charachteristics of the sinter ferrite medium film aging based on a metal was simulated and analysed using Ansoft Designer which is on MOM and resolution methods.The metal surface was coated with a medium layer of thickness 2 mm and diameter 10mm,which has relative permittivity εr=20,relative permeability μr=1.2,dielectric loss tangent 0.45,and magnetic loss tangent 10,and a crack of 5 mm length and 1 mm width on the surface.Plane wave slope incidence is used for calculation and analysis,and the conclusions that infection is obvious for stealth due to of coating sinter Ferrite medium performance variaty in 812 GHz is obtained.