<p>Dopamine (DA), a crucial neurotransmitter, plays a pivotal role in various physiological and pathological processes, making the development of simple and novel detection methods highly significant. Herein, a facile ratiometric platform was constructed for ultrasensitive detection of DA based on the nanozyme facilitated in-situ fluorogenic reaction. Firstly, GMP-Ce⁴⁺ CPs with enhanced oxidase-like activity were produced via an extremely simple one-step self-assembly method, which could efficiently initiate the fluorogenic reaction between DA and β-naphthol (β-NAP). Relying on the enhanced catalytic ability and the specificity of the fluorogenic reaction, a ratiometric platform was established by introducing rhodamine B (RhB) as a fluorescence reference. The proposed ratiometric method exhibited wide linear range (0.001-30 µM), ultra-high sensitivity (LOD 0.6 nM) and great selectivity. Finally, the designed method has been used for DA assay in practical health blood serum (HBS) samples with satisfactory results, demonstrating its potent analytical applicability in the biosensing field.</p> Graphical Abstract <p></p>