Properties　of　Cp(4)An　and　COT(2)An　(Cp-=C5H5-,　COT2-=C8H82-,　An=U(IV),　Pu(IV))　species　both　in　gas　phase　and　tetrahydrofuran　(THF)　solution　are　systematically　studied　by　DFT　(density　functional　theory).　The　solvent　effect　of　THF　is　simulated　by　a　conductor-like　polarized　continuum　model　(CPCM).　Theoretical　calculations　show　that　the　binding　energies　of　the　complexes　are　in　the　order　of　COT2Pu＞COT2U＞Cp4Pu＞Cp4U.　Solvent　effects　decreased　binding　energies　of　the　structures.　The　optimized　geometry　structures　and　the　IR　spectra　for　the　complexes　in　gas　and　aqueous　phase　are　in　accordance　to　the　available　experimental　data　very　well.　Detail　studies　on　MO　energy　levels　for　Cp(4)An　and　COT(2)An　with　An=U(IV),　PU(IV)　calculated　with　rsc　ecp　indicate　that　COT2U　and　CP4U　favors　triplets　f(phi)(2)　and　f(phi)(2)　configuration　respectively,　meanwhile,　COT2Pu　and　Cp4Pu　favor　quintets　f(sigma)(1)f(pi)(1)f(phi)(2)　and　f(sigma)(3)f(delta)(1)　configuration　respectively.