Abstract: A new type of stable fluorescent cadmium complex, Cd(C3H4N2)4(C10H6O6S2)2 [abbreviated as Cd(Im)4(1,5-NDA)2], was synthesized by solvothermal method using cadmium nitrate tetrahydrate as the metal source, 1,5-naphthalenedisulfonate (1,5-NDA2-) and iImidazole (Im) as the main and auxiliary ligands. The compound was characterized by X-ray single crystal diffraction and thermogravimetric analysis. The X-ray single crystal diffraction results indicated that the compound belonged to the Monoclinic crystal system with the C1c1 space group, and the central ion Cd(II) was located in the distorted octahedral structure. The thermogravimetric analysis results proved that the compound had good thermal stability. The fluorescence properties of Cd(Im)4(1,5-NDA)2 were investigated. The solid-state fluorescence spectra showed that the compound had good fluorescence properties, and its fluorescence emission mainly came from the π-π* transition of the ligands. The orbital contributions of the excited state of the complex were calculated using the time-dependent density functional theory (TD-DFT). The fluorescence quenching experiments results indicated that Fe3+ had a significant quenching effect on the fluorescence intensity of the complex, and the detection limit of Fe3+ recognition by the complex was 0.46 μmoL/L. By using the multi-technology combined approach, the possible fluorescence quenching mechanism of Fe3+ on Cd(Im)4(1,5-NDA)2 was speculated. The results of ultraviolet-visible absorption tests indicated that energy resonance transfer (FRET) occurred between Fe3+ and Cd(Im)4(1,5-NDA)2. The characterization results of powder X-ray diffraction, infrared spectroscopy, inductively coupled plasma mass spectrometry, energy dispersive spectroscopy and X-ray photoelectron spectroscopy showed that there were interactions between Fe3+ and N atoms on Cd(Im)4(1,5-NDA)2. In summary, the fluorescence quenching mechanism of Fe3+ on Cd(Im)4(1,5-NDA)2 is a dual-path cooperative quenching: FRET between Fe3+ and the complex and the interactions between Fe3+ and the N atoms on the complex.