Abstract: By static adsorption experiments, the effects of pH, adsorption time, uranium’s initial concentration, adsorbent dosage, chaff size and temperature on the biosorption capacity of chaff for uranium were studied. The unit mass of adsorption process was analyzed in thermodynamics and kinetics, and the adsorption mechanism was analyzed by infrared spectroscopy and scanning electron microscopy. The results show that the adsorption capacity for uranium on chaff increases with the increase of initial concentration of uranium, decreases with the increases of the amount of chaff, and increases with the increase of temperature; the best adsorption is obtained at pH＝3, when the particle size is in 100-120 mesh; the adsorption equilibrium is achieved in 60 min. At 25 ℃, the saturated adsorption capacity q_max is up to 15.14 mg/g. The adsorption of uranium on chaff follows Langmuir adsorption isotherm, and is in line with quasi-second order kinetic equation. IR micrograph before and after chaff adsorbed uranium indicates that the chaff is mainly composed of hydroxyl, carbonyl, aromatic and carbohydrate, and the main way of adsorption of uranium is the ion exchange or surface complexing.