A fluorescent molecular probe (L) based quinoline schiff base was synthesized by the condensation reaction of 8-hydroxyquinoline-2-carboxaldehyde and salicylhydrazide. The molecular structure of the probe L was determined by FT-IR, 1H NMR, 13C NMR and ESI-MS. The recognition performance of probe L was studied by absorption and fluorescence spectra in DMSO solution. The probe L and Fe3+ could form a 1: 1 complex L-Fe, which binding constant is 4.6*104 L/mol. Through the quenching of probe fluorescence caused by the formation of the above complexes, Fe3+ could be selectively recognized in common metal ions, and the detection limit is 6.8* 10-8 mol/L. Furthermore, the L-Fe complex was used as a probe to achieve highly selective fluorescence enhanced recognition of oxalic acid, and the detection limit is 1.3*10-7 mol/L. This method could be used to detect oxalic acid in vegetables samples.