The isothermal adsorption and the adsorptive mechanism of aflatoxin B-1 (AFB(1)) on calcium montmorillonite (Mont) were studied in vitro trials. The maximum amounts of AFB(1) on Mont in aqueous solution at 2 and pH 8 were 613.5 and 628.9 mu g of AFB(1)/g of Mont, respectively. The structure of AFB(1)-Mont was measured by x-ray diffraction and infrared absorption spectrum. The results suggested that the mechanism of AFB(1) on Mont was AFB(1) sorbed onto the edge of Mont by a double hydrogen bond, and AFB(1) molecules did not penetrate into the interlayer area of Mont. The Mont, when added to the diet of broiler chicken at 0.5%, significantly diminished the adverse effects of feeding 200 mu g of AFB(1)/kg of feed. And the concentrations of Ca, P, Cu, Fe, Zn in the broiler bones were not affected by AFB, and Mont, but the concentrations of Mn, Pb, and F were decreased by Mont.