In this study, the zeolitic imidazolate framework (ZIF-8) and glutathione silver nanoclusters (GSH-AgNCs) were assembled by the in situ synthesis method to form nanomaterials (GSH-AgNCs-ZIF-8). Meanwhile, a luminescent functional assembly of nanocomposites with adjustable potentials and luminescence enhancement was gained through innovative mixing of the luminophores tetracarboxyphenyl zinc porphyrin (TCPP-Zn) and GSH-AgNCs-ZIF-8. Composition and morphology of the materials were studied by electrochemistry and spectroscopy techniques. The blended material was used as high-efficiency luminophore to build the electrochemiluminescence (ECL) sensing system for iodide ion (I − ) detection whose ECL mechanism has also been studied in depth. Under optimization conditions, ECL sensors showed excellent responses to I − in the linear range from 10 pM to 10 μM. This detection method showed selectivity, stability, and sensitivity. Moreover, it achieved relatively satisfying results to iodide ion detection in cola, milk, nori, and urine samples. This research not only develops and applies functional nanomaterials, but also establishes an ECL sensor system and provides ideas for the detection of micromolecules in food and clinical testing.