In　this　paper,　in　situ　Fourier　Transform　Infrared　Spectroscopy　(FTIRS)　is　used　to　study　the　electro-catalytic　oxidation　mechanism　of　shikimic　acid　(SA)　at　a　copper　electrode　in　H2O　and　D2O　solution,　respectively.　As　the　potential　is　applied　between　0.1　V　and　0.2　V　vs.　SCE,　SA　is　oxidized　to　3-dehydroshikimic　acid　(DHS).　Then　a　significant　change　appeared　when　the　potential　is　scanned　from　0.3　V　to　0.8　V,　DHS　is　decomposed　to　transaconitate　and　formate.　As　the　potential　is　over　0.9　V,　formate　is　further　oxidized　to　CO2.　Density　functional　theory　(DFT)　calculation　of　the　IR　spectra　is　in　good　agreement　with　the　experimental　observation.　The　adsorption　of　transaconitate　through　carboxyl　on　copper　electrode　is　also　evidenced　by　p-　and　s-polarized　radiation　in　FTIRS.　©　2011　Elsevier　Ltd.　All　rights　reserved.