The binding equilibrium of potassium perfluorooctanesulfonate (FC95) to DNA was studied by UV spectra and resonance light scattering technique in the present paper. It was found that the interaction resulted in strongly enhanced resonance light scattering signals characterized by the RLS peak at 370 nm. The results indicated that the conformation of the DNA has changed during the interaction because the micro environment of DNA changed. The binding constant K-f and the number of binding n were calculated according to the equilibrium equation, which was established based on the data of the resonance light scattering measurements at 370 nm. It was found that the binding K-f and the number of binding n were 6.02x10(3) and 2.0, respectively. (C) 2010 Elsevier B. V. All rights reserved.