The　interaction　of　cyanide　(CN)　with　different　sites　of　Pt(100)　surface　is　studied　by　using　density　functional　theory　(DFT).　Pt-14　cluster　is　used　to　simulate　the　surface.　The　present　calculations　show　that　the　top　site　is　more　favorable　than　other　adsorption　sites　when　CN　is　bonded　to　the　surface　via　the　carbon,　and　the　calculated　C　-　N　stretching　frequency　is　blue　shift　in　agreement　with　the　experimental　results.　For　other　adsorption　sites　on　the　Pt　(100)　surface,　the　calculated　C　-　N　stretching　frequencies　are　red　shift.　When　CN　molecule　adsorbed　on　Pt(100),　the　charge　transfer　between　the　sigma,　and　pi　electron　of　CN　molecule　and　the　substrate　led　to　the　variation　of　CN　vibrational　frequency.