The di-O-methylcurcumin L as a molecular probe was directly synthesized by using curcumin and iodomethane.The title compound was characterized by X-ray single-crystal diffraction,1H NMR，13C NMR and ESI-MS.The crystal structure of the compound belongs to monoclinic system with a space group of C2/c.The cell parameters were as follows：a=22.317(6) nm,b=8.703 8(19) nm，c=23.039(5) nm，β=93.378(10) °，V=4 467.4(18) nm3，Z=4，Dc=1.206 g?cm-3，F(000)=1 720，μ(MoKα)=0.088 mm-1，R=0.080 9，ωR=0.216 3.The probe L exhibited a selective and sensitive absorption response toward Fe3+ over a wide range of metal ions in ethanol-water solution(9∶1，Tris-HCl buffer，pH 7.2).The results of ultraviolet titration and mass spectrometry showed that the probe L and Fe3+ formed a 1∶1 complex,and the association constant K was determined to be 1.089×106 L/mol.The mothod showed good linearity(r2= 0.997 8) for Fe3+ concontration in the range of 5.5×10-6– 3×10-5 mol/L with a limit of detection of 2.2×10-6 mol/L.