In this paper, the association of anionic dyes Coomassie brilliant blue G250 (CBBG250) with cationic surfactant CTAB was studied by spectroscopy. It can be seen from the spectra that the characteristic absorption peak of CBBG250 is changed obviously by the addition of CTAB. We establish a reasonable association reactions physical model to obtain a series of thermodynamic parameters such as the equilibrium constant, Gibbs free energy and entropy of the association reaction at different temperatures. The experimental results show that the elevated temperature is favorable for the association reaction. The higher the temperature, the greater will be the degree of molecule association.