[en] Graphical abstract: A novel Tb complex was prepared by a simple way used sulfonate ligands owing to their broaden applications in various areas and abundant coordination modes, and the compound showed excellent electrochemiluminescence properties under the optimized conditions. Then a facile and fast response ECL senor was fabricated for sensitive and specific detection of Cd²⁺ based on effective quenching of ECL signal after addition of Cd²⁺. The low cost, facile preparation and simple instrument offer a alternative strategy for detection metal ions in real samples, and broaden the application fields of ECL system. - Highlights: • A novel Tb complex was synthesized with the ligand of pyridine-3-sulfonic acid, which has excellent ECL performance. • A simple and straightforward ECL senor was constructed for sensitive and selective detection of Cd²⁺. • Low cost, fast analysis and facile operation offered a promising method to detect the Cd²⁺ in real samples. - Abstract: In this paper, we report a novel rare earth metal complex with the weak ligand of aromatic sulphonic acid (pyridine-3-sulfonic acid, 3-pSO₃H), and characterized by FT-IR, UV–vis, energy-dispersive X-ray spectroscopy (EDX), electrochemiluminescence spectra, etc. Then an excellent electrochemiluminescence (ECL) signal was observed with K₂S₂O₈ as the coreactant in NaAc-HAc buffer solution. For another thing, the electrochemical properties of the compound have been thoroughly investigated in acetonitrile solution, the possible ECL reaction mechanism was proposed as well. Furthermore, a simple and straightforward ECL platform was reported for sensitive and selective detection of Cd²⁺ due to the effective quenching after addition of Cd²⁺. Other heavy/transition metal ions do not interfere with the sensing. The limit of detection is determined as 0.13 nM, the results suggested that as-prepared complex could be a promising material for developing ECL senors to detect the Cd²⁺ rapidly indwell in environmental and practical samples.