The　multicomponent　heteropoly　compounds　[Me4N](1+x)　[SiVxMoyW12-x-yO40].　n　H2O　with　Keggin　structure　have　been　synthesized　and　characterized　by　FTIR.　The　vibrational　frequencies　of　containing-oxygen　bonds　(Si-O-a,　M　=　O-d,　M-Q(b)-M　and　M-O-c-M)　in　these　heteropoly　compounds　have　been　studied.　The　vibrational　frequencies　v(as(M=Od))　and　v(as(M-Ob-M))　are　demonstrated　to　explain　why　the　acidify　of　the　heteropoly　compounds　becomes　weaker　and　the　oxidative　ability　becomes　stronger　when　W　atoms　are　substituted　by　V　atoms.　The　rule　of　the　change　is　similar　with　[PVxMoyW12-z-yO40]((3+c)-).　In　addition,　the　acidity　of　P　series　is　stronger　than　the　acidity　of　the　corresponding　Si　series.