A predictive model is developed to describe the salt effects on the adsorption equilibrium of protein to Cibacron Blue-modified agarose gel (Sepharose CL-6B). This model assumes that, with the addition of salt, a fraction of dye-ligand molecules will lodge to the surface of the agarose gel resulting from the induced strong hydrophobic interaction between the dye ligands and agarose surface. This leads to a decrease in the dye ligands accessible to protein adsorption and consequently decreases the adsorption capacity of protein. The effect of salt on the dye-ligand lodging is presented by the equilibrium between salt and the dye ligands. Combined with the basic concept of steric-mass action theory, which considers both the multipoint nature and the macromolecule steric shielding of protein adsorption, an implicit isotherm of the protein adsorption equilibrium on Cibacron Blue 3GA-modified Sepharose CL-6B is formulated, involving salt concentration as a variable. Good agreement between experimental data and the predicted adsorption isotherms for single-component protein systems has been demonstrated, and fairly good matching between the predicted and experimental data for the binary adsorption of bovine serum albumin and bovine hemoglobin is obtained under most conditions. This model is expected to be useful in the design and optimization of the salt-gradient elution process of dye-ligand affinity chromatography.