The mechanism of interaction between γ-cyclodextrin-neutral red（γ-CD-NR） inclusion complex and herring sperm DNA was studied by UV-Vis and fluorescence spectra.The results suggest that the intercalation and electrostatic binding should be the two major modes for the interaction between γ-CD-NR and DNA.It were confirmed by molar ratio method and double reciprocal method that the binding ratio of nγ-CD∶nNR=1∶1 and the binding constant of Kf=2.08×103 L·mol-1.While the binding ratio of nγ-CD-NR∶nDNA=4∶1 and the binding constant of K■25 ℃=2.11×106 L·mol-1.Thermodynamic function computation demonstrated that entropy（ΔrS■m） is the primary driving power of the interaction between γ-CD-NR and DNA.The results suggest that there are competitive action between γ-CD-NR inclusion complex and AO when they interact with DNA.