Abstract: Fourteen dimethyl sulfoxide complexes of lanthanide and yttrium nitrates were prepared and analysed. The IR and Raman spectra of the complexes were studied systematically. The bands have been assigned and discussed. The S=O and Ln—O stretching vibration modes split in the heavy lanthanide complexes, which was attributed to the resonance coupling of same groups. The group symmetry changing causes the split of nitrate combination frequency 1775 cm~(-1). The coordination mode of nitrate can be identified in the complexes. The Ln—O stretching mode was suggested. The generic form of “inclined W” between the Ln—O stretching frequency and the L-value of rare earthes was discovered.