In this paper, the adsorption behavior of humic acid (HA) on kaolin was investigated and the characteristics of HA-kaolin complexes were studied by means of X-ray diffraction pattern,TGA and IR. According to the results obtained,when the HA-kaolin complexes are washed six times,the HA can be stably combined with the kaolin; the Fruendlich-type equation can describe the adsorption isotherm of HA on kaolin well,and the K_f of HA on kaolin is 0.857; there exist apparent absorption peaks of hydrocarbon in the IR; chemical adsorption plays a major role in the interaction between HA and kaolinite, and the adsorption behavior mainly takes place on the hydroxyl sites of aluminum.