The present article deals with the study of protein (gelatin and casein) adsorption of electodialyzed soil colloids from Chernozem, Drab soil and Red earth, and clay minerals from bentonite, kaolinite and ground mica. The stuctural type of clay minerals affects the amount of adsorption of protein by the order of type 2:1 >type 1:1. The protein adsorption of soil colloids seems also to be related with the composition of clay minerals and the status of exchangeable rations. The less the ration exchange capacity of bentointe, the less will be the adsorption of gelatin. With the same bentonite, the increase of the amount of adsorption of gelatin results in the decrease of exchange capacity.The amount of adsorption of gelatin by bentonite saturated with mono-valent exchangeable rations is greater than that saturated with divalent rations, which in turn is again greater than that saturated with trivalent rations. Alternative treatment of drying and moisting increases significantly the adsorption of gelatin. The protein adsorption of soil colloid is explained by the reaction of ration exchange between the negatively charged clay and the positively charged radicals of the protein micelles. However, the nonpolar adsorption also occurs in the protein adsorption of soil colloids. X-ray diffraction analysis showed that part of the gelatin can be inserted into the (001) spacings of montmorillonite. The decrease of diffraction intensity of clay is due to the formation of hydrophobic aggregates.