The geometry and excitation spectra of third-row transition metal hexafluorides are discussed based on the SFand SO-X2C MRCI theory. The electronic states involved in the excitation spectra are assigned based on the double group. Including the SOC variationally in the X2C Hamiltonian allows for analysis of SO splitting at the MO level. Our schematic MO diagram can effectively demonstrate how the SOC influences the structures of the metal hexafluorides. From the comparison between the SF and SO results, the SOC dramatically changes a well-known picture of the ligand field without the SOC: triply degenerate t 2g orbitals are splitting to one e 5/2,g and doubly degenerate u 3/2,g orbitals. The SO effect should not be obtained as a correction using a single-reference method such as DFT in molecules with multi-reference characters. The SO splitting destroys the degeneracy of the MOs at the SF level and quenches the JT distortion. The excited states at the SO level cannot simply correlate to those at the SF level due to the strong SOC. A strong SO effect is also observed in the population analysis.