A naphthalimide Schiff base fluorescent probe L was designed and synthesized with 4-bromo-1,8naphthalene dicarboxylic anhydride as raw material. Its structure was characterized by H-1 nuclear magnetic resonance ( NMR),C-13 NMR, infrared ( IR) spectroscopy and high resolution mass spectrometry ( HRMS). In the CH3CN-H2O ( 75 : 25, V / V, 20 mmol/ L HEPES, pH = 7. 4) solution, the probe possessed good selectivity and sensitivity to Cu2+ and with a detection limit as low as 0. 37 mu mol/ L. The stoichiometric ratio of L to Cu2+ was 1 : 1, and the complex L- Cu2+ had high selectivity, good sensitivity, low detection limit of 0. 56 mu mol/ L ( 0. 09 mu g/ mL) and naked eye recognition for detection of glyphosate by ligand replacement menthod. In addition, the L-Cu2+ was succesfully used in detection of glyphosate in actual water samples, which indicated that the proposed probe had potential application in the field of environmental detection. Keywords Fluorescent probe; Schiff base; Naphthalimide; Copper ion; Glyphosate