As part of the systematic research on the interactions between the components of the polyacrylonitrile-based electrolytes (plasticizer-lithium salt-polymer), the Raman and IR spectra of pure dimethylsulfoxide (DMSO) and DMSO containing different molar ratios of LiClO4 have been studied. By analyzing the Raman and IR spectra of the S=O stretching band, it is found that the introduction of LiClO4 to pure DMSO leads to the dissociation of the cyclic dimers. Li+-DMSO associates are formed through the interaction between Li+ and the S=O group of DMSO. The spectral changes of the S=O bending bands and the C-H stretching bands indicate that the interaction between the Li+ ion and the molecule not only breaks down the self-association of the solvent, but also, by way of the induction effect, perturbs the electronic nebula around the C-H bond. It seems that the effect of the ClO4- anion on the molecules is too weak to be observed by the vibrational spectroscopy.