This　Letter　presents　a　new　technique　for　measuring　the　variation　of　the　material　properties　along　the　thickness　in　a　freestanding　inhomogeneous　thin　film.　The　analytical　results　reveal　a　simple　relation　between　the　material　properties　and　the　set　of　cut-off　frequencies　of　Lamb　waves.　The　influence　of　the　graded　properties　on　the　variation　of　cut-off　frequencies　in　three　different　kinds　of　models,　including　artificial　FGM　model,　sub-surface　damage　model,　and　nano-porous　thin　film　model,　is　discussed.　These　results　provide　theoretical　guidance　for　characterizing　the　material　property　variations　of　MEMS/NEMS.　(C)　2010　Elsevier　B.V.　All　rights　reserved.