The fluorescence (transmission) spectra of solid electrolyte polyacrylonitrile (PAN)/dimethylformamide (DMF)/LiClO4 with different combinations of its components have been measured with a radiation line at 280 nm. A fundamental analysis of the spectra indicates that interactions exist between the Li+ ions and the oxygen and/or nitrogen atoms of DMF. The interaction between the O atoms of DMF and the N atoms of the nitrile of PAN has also been observed. However, the interaction between LiClO4 and PAN is undetectable by the fluorescence spectra. This might imply that the transportation mechanism of the Li+ ions in polymer electrolytes is related not only to the polymer but also to the plasticizer in which the lithium salt is disserved.