In this paper, characteristics of adsorption of humic acids from soils with different fertilization (for 17 years) by Ca-saturated montmorillonite was investigated. The main results showed that adsorpton isotherms of humic acids by montmorillonite could be described by singe surface Langmuir, Freundlich and double-surface Langmuir equations. Adsorption amount of humic acid increased as temperature rose, while adsorption strength decreased. Applying organic material could increase adsorption amount and strength of hunuc acids compared with no fertilizer and chemical fertilizer. The double-surface Langmuir equation indicated that humicacid adsorption by montmorillonite had two energy sites-the high and the low levels. Adsorption of humic acid on the high energy site was mainly chemical absorption which was an endothermic reaction. On the other hand, the adsorption of humicacid on the low energy site was mainly physical absorption, which was an exothermic reaction. With application of organic material, absorption of humic acids on the high energy site became weaker and that on the low energy site absorption became stronger compared with no fertillizer and chemical fertilizer.