Laboratory batch experiments were conducted to study the sorption and desorption of cadmium (Cd) in loess improved by composted sludge. The results showed that there was significant difference in change rules of adsorption isotherm before and after 20 mg/L of the initial Cd concentration. Cd absorption behavior could be described by Freundlich equation and relation between adsorption and desorption of Cd could be described by exponential function. Stable adsorption capacity increased with the concentration of composted sludge in soil samples increased. The organic matter in soil samples has the greatest contribution to the stable ability of Cd.