Atomic　force　acoustic　microscopy　(AFAM)　has　been　developed　in　order　to　evaluate　the　mechanical　properties　of　the　material　at　the　nanometer　scale.　The　SiOx　film　on　the　silicon　wafer　was　prepared　successfully　by　plasma　enhanced　chemical　vapor　deposition　(PECVD).　In　order　to　characterize　the　elastic　property　of　the　SiOx　film,　the　images　of　cantilever　amplitude　were　visualized　when　the　sample　was　excited　at　100kHz　and　400kHz　frequency.　The　acoustic　amplitude　images　also　were　discussed　at　the　different　exciting　amplitudes.　The　results　showed　that　the　acoustic　amplitude　images　can　provide　the　information　about　local　elasticity　of　the　materials.