In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (II) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultane- ously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fad- ing reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L?1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70 -3.10 μg·L?1 for RRS method. Among the above three methods, the RRS method has the highest sen- sitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addi- tion, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods. In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin , 其它 结束 在 erythrosine to form the ion association complexes. They can result in the changes of the absorption association spectra. Simultaneously- ously, erythrosine fades obviously and the maximum fading wavelength is located at The new assay reagents for these drugs are developed. Thus, new spectrophotometrytries for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also has high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg · L -1. In addition, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and the The detection limits for fluoroquinolone antibiotics are in the range of 1.70 - 3.10 μg · L -1 for RRS method. Among the above three methods, the RRS method has the highest sen- sion sitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addi- tion, the mechanism of reactions were discussed by density function theory ( DFT) and AM1 methods.