Semiempirical　quantum　chemistry　method　AM1,　Hartree-Fock　method　at　3-21G*　basis　set　level　and　density　functional　method　at　B3LYP/6-31G(d)　basis　set　level　were　employed　to　study　the　total　35　tautomers　with　planar　conformational　isomer　of　molecule　uric　acid.　The　calculated　results　show　that　the　tricarbonyl　tautomer　is　the　most　stable　and　the　trihydroxy　tautomer　is　the　most　unstable　of　all　35　tautomers,　which　is　in　agreement　with　the　experiment.　The　bond　lengths　and　bond　population　analysis　are　presented　in　this　paper.　The　average　C-N　bond　lengths　became　shorter　when　the　amount　of　hydroxy　groups　in　tautomers　increased　and　the　average　C-C　bond　lengths　had　no　remarkable　chang　in　all　tautomers.