Oxygen transfer reactions involving o rganorhenium oxides have been extensively investigated because of their relatively stable structures, versatile valences, rich coordination types and unique catalyti cp atterns. Here, a systemati c density fun c tional studies on the structure and spectrum of organorhenium oxides have been presented. It has been found that b ond length of Re=O follows the sequence that Cp*ReO 3 >C p ReO 3 >NH 2 ReO 3 >CH 3 ReO 3 >HOReO 3 >C l ReO 3 FReO3 , which is in parallel with the dipole moment of oxid ized rhenium but in anti p arallel with the vibrational frequency of the Re= O bond. However, the bond strength of Re=O has a different trend, CpReO 3 C p *ReO 3 NH 2 ReO 3 HOReO 3 <FReO 3 <C lR eO 3 CH 3 ReO 3 , which does not correlate well with the change of the Re=O bond length. Additionally, the strength of Re=O could be subtly tuned by various ligands such that oxidized r henium can play a keyrole in the catalytic oxidation processes.