Abstract: A novel composite fluorescent probe, FSS@ZIF-8, was successfully synthesized via a one-pot soaking method by encapsulating fluorescein sodium (FSS) within the ZIF-8 framework. In aqueous solution, the probe exhibited strong fluorescence and achieved highly selective fluorescence quenching for terbuthylazine-2-hydroxy, a triazine herbicide, even in complex matrices. It demonstrated an impressively low detection limit of 3.28×10⁻⁶ M and a Stern-Volmer quenching constant of 2.19×10⁴ M⁻¹. A linear relationship between the fluorescence quenching intensity and the analyte concentration validated its capability for quantitative analysis. Notably, FSS@ZIF-8 exhibited remarkable fluorescence stability across various solvents and over a broad pH range (4-12). Its fluorescence intensity remained stable under diverse environmental conditions and during prolonged storage (up to 10 days), enabling rapid room-temperature detection of terbuthylazine-2-hydroxy. The dynamic correlation between the probe’s fluorescence response and the analyte concentration highlights its potential for sensitive monitoring of environmental pollutants. This study establishes an efficient, robust, and highly sensitive fluorescent platform for detecting triazine herbicides, while providing valuable insights into the design of MOF-based fluorescent sensors.