The interaction between polyvinylpyrrolidone (abbreviated as PVP) and europium benzenesulfonate was investigated by using temperature-dependent FTIR and fluorescence spectra. Europium compounds show strong coordination ability with amide groups of PVP. In order to remove the undesired H—O—H scissoring bands from the adsorbed water in FTIR spectra, temperature-dependent FTIR was utilized to reveal the spectral behavior of amide Ⅰ band after being coordinated with europium ions from europium compounds. As a result, the bond order of the carbonyl groups decreased, leading to a red-shift of amide Ⅰ band in the FTIR spectra. Furthermore, fluorescence spectra demonstrate that the interaction between PVP and europium benzenesulfonate enhanced the solubility of europium benzenesulfonate in chloroform. As a matter of fact, europium benzenesulfonate, which is insoluble in chloroform, becomes soluble in chloroform containing 10 Wt% PVP. In the fluorescence spectrum of europium benzenesulfonate crystals, only the f—f transition peaks of europium ions can be found. However, the emission peak of the π*—π transition of benzenesulfonate group appears in concentrated aqueous solution of europium benzenesulfonate. The phenomenon shows that part of benzenesulfonate undergoes decomplexation from europium benzenesulfonate complex and isolated benzenesulfonate occurs in the aqueous solution. Energy transfer pathway from excited triplet state of benzenesulfonate to europium ions is blocked in isolated benzenesulfonate. As a result, π*—π transition band of benzenesulfonate can be observed in the florescence spectrum. The decomplexation provides larger coordination space around europium ions, which favors the coordination between europium benzenesulfonate and PVP.