A DFT(density functional theory)/TDDFT(time-dependent density functional theory) investigation is performed to study the ground-state geometries, electronic structures, and absorption spectra of twelve ruthenium(II) thiosemicarbazone complexes [Ru(CO)(C)(Ln)], where Ln=derivatives of dibasic tetradentate Schiff-base ligand and X=AsPh3/PPh3/Py. The ground-state geometries are optimized at the B3LYP/6-31G(d)-LANL2DZ level, and the spectra are simulated by means of TD-B3LYP/6-31G(d)-LANL2DZ method on the basis of the optimized geometries. The influence of principal and secondary ligands (Ln and X) on transition characters and absorption peak positions is evaluated.