<p>Fluorescent hydrogels have attracted much attention due to their excellent and unique photoluminescent properties, which makes it very necessary to explore their luminescent properties. In this study, a three-dimensional hydrogel system of polyacrylamide-konjac mannan − 2,6-pyridine dicarboxylic acid (PAM-KG-Ln) was constructed using the rare earth element Eu as the luminescence unit, and a series of PKL: <i>x</i>Eu³⁺ fluorescent hydrogels were prepared by in-situ polymerization. The prepared hydrogels had excellent luminescence properties and a color purity of 99.4%. It was found that the strongest emission peaks of PKL: <i>x</i>Eu³⁺ fluorescent hydrogels were located at 700&#xa0;nm under excitation at 295 and 398&#xa0;nm., which were derived from the ⁵D₀→⁷F₄ transition. In addition, it was found that the fluorescence quenching phenomenon occurred under the ultraviolet lamp with the increase of Eu³⁺ doping concentration, and then the spectral analysis combined with Van Uitert modeling revealed that the ⁵D₀ energy level quenching mechanism of Eu³⁺ was dominated by electric dipole-electric dipole interaction (Q ≈ 6), which provides a new paradigm for the design of dynamic fluorescent hydrogels, and is expected to promote the development of applications such as high-resolution biological probes and stimuli-responsive soft drives.</p>