A novel cellulose derivative, maleyl ethyl cellulose (MAEC), was synthesized. MAEC could be dissolved in acetic acid (AA) and formed cholesteric liquid crystalline solutions. The critical concentration of the phase transformation from the isotropic phase to the liquid crystalline one decreased with increasing the degree of substitution of maleic acid. MAEC formed complexes with the rare earth metal ion EU3+, which resulted in fluorescence in the system. The fluorescent spectrum of the system was influenced by the complexion state of EU3+ with MAEC and AA. The variation of the molecular interactions between polymer chains and between the polymer chains and the solvents in the formation of the liquid crystalline phase, and the phase transformation with the variation of the concentration in the solutions, were reflected by the variation of R = I-613/I-591 in fluorescent spectra. It was found that the interactions between polymer chains are enhanced in the initial stage of the formation of the liquid crystalline phase. But the interaction between polymer chains decreased when the concentration was very high and, at this time, the rigidity of the polymer chains plays a principal role in the formation of the liquid crystalline phase.