A ratiometric fluorescence sensor based on lanthanide metal-organic frameworks(MOFs) was synthesized for the detection of naproxen.A ratiometric fluorescent sensing material Eu-MOF,with Eu3+ as metal node and 1,3,5 benzenetricarboxylic acid as ligand,was synthesized by ultrasound synthesis method.The morphology characteristics and optical properties of this Eu-MOF,as well as its detection of naproxen were studied.The Eu-MOF showed dual emission from ligand and Eu3+ under the single excitation.The fluorescence emission of naproxen coincided with the fluorescence emission of Eu-MOF at 375 nm.There was an inner filter effect between Eu-MOF and naproxen.Therefore,the fluorescence emission increased gradually at 375 nm,but weakened gradually at 623 nm with the addition of naproxen,so that the ratiometric fluorescence detection of naproxen could be achieved.There was a good linearity of Eu-MOF for naproxen in the range of 007-23 μmol/L with a detection limit(LOD) of 0039 μmol/L.The Eu-MOF showed good selectivity and anti interference ability in the detection of naproxen.Thus,it is a superior material for detection of naproxen in actual samples.