The interaction between naproxen and cyclodextrin was studied by two-dimensional diffusion ordered（2D-DOSY) NMR spectroscopy.Influences of different factors on the self-diffusion coefficient and the equilibrium constant were investigated.The results showed that the increase of temperature,water content,pH and ionic strength had more influence on the self-diffusion coefficient of the guest than that of the host，which could increase the equilibrium constants.The inclusion interaction was the strongest in a solution of pH 9.0.The results of thermodynamic analysis showed that the inclusion process was spontaneous and endothermic entropy-driven process,and the main active force was the hydrophobic force.