Poly(vinyl acetal) from poly(vinyl alcohol) and 4-dimethylaminobenzaldehyde (DMAB) is synthesized. Fluorescence behavior of the polymer is investigated in acetic acid glacial (HAc), dimethylsulfoxide (DMSO), and dimethylformamide (DMF) solvents. Fluorescence emission intensities of the polymer solutions are different with the change of concentration. The result suggests that the maximum fluorescence emission intensities of the polymer solutions depend on the optimal concentration of the polymer. It has been found that the fluorescence intensity of DMAB is dramatically lower than that of the polymer in the same chromophore concentration, and such phenomenon is termed as structural self-quenching effect (SSQE). The strong fluorescence of the polymer can be quenched by adding electron-deficient monomers which have no chromophore moieties such as lactic acid, adenine, etc., and their Stern-Volmer constants are determined. It is observed that the higher the electron deficiencies of the quenchers, the higher the Stern-Volmer constants, which means stronger quenching effect. The result indicates that the polymer can recognize these biologic small molecules.