A complex composed of ciprofloxacin and terbium (Tb3+) in the solution of acetic acid-sodium acetate buffer (pH 6.2) was studied by fluorescence spectroscopy and ultra-violet absorption spectroscopy. The emission peak of Tb3+ appeared at 490, 545, 590 nm, (the sensitized fluorescence was enforced mightily) and the intensity of 545 nm emission peak was increased obviously. In its acute emission spectrum, the strongest emission peak of Tb3+ was at 545 nm, which was close to the wavelength of the biggest absorption peak of RB, 552 nm. Therefore, as the basic dye rhodamine B(RB) was added, the fluorescence intensity of 545 nm emission peak decreased regularly, indicating that there was a great quenching process. The result showed that the course was statistic. Based on the mechanism of the Förster energy transfer, the efficiency of energy transfer and the distance between the acceptor RB and the complex were found. Thereby, it was indicated that the course of action was single static quenching and the mechanism of quenching was based on energy transfer.