A novel reaction-based probe (IV), 2-(4-(dimethylamino)phenyl)-4-oxo-4H-chromen-7-yl picolinate was designed and synthesized by utilizing 2-picolinate as the recognition unit. The probe was identified by 1H NMR, 13C NMR, MS and elemental analysis, and it exhibited excellent selectivity for Cu2+ among many common metal ions in HCl-Tris buffer/CH3CN (3:2, V/V) solution, its fluorescence was considerably enhanced by the addition of Cu2+ at room temperature in 5 min, and the color of the solution was changed from red to yellow which can be identified by naked eyes. A linear relationship was observed between the fluorescence intensity and the concentration of Cu2+ in the range of 0 ~ 2.0×10-5 mol·L-1. The detection limit of IV for Cu2+ is 1.67×10-8 mol/L and it can be applied in water quality detection. Mechanism study suggested that Cu2+ promoted the hydrolysis of IV via the catalytic sensing cycle, generating a highly fluorescent N,N-dimethylamine flavonoid (III).