The aim of this work was to study the influence of phosphate and citrate, which are common inorganic and organic anioilS in soils, on the adsorption of acid phosphatasc by kaolin, goethite and tile colloids separated fi'onl yellow-brown soil (YBS) and latosol (LS) in central-south China. The YBS colloid has the major clay mineral composition of 1.4 nm mineral, illite and kaolinite while the LS colloid mainly contains kaolinite and oxides. Thc adsorption isotherm of acid phosphatase on the exanlined soil colloids and minerals fitted to the Langmuir model. Tbe amounl of enzyme adsorbed in the absence of ligands was in the order of YBS colloid>LS colloid>kaolin≈gocthite. In the presence of phosphate or citrate, the amounts of the enzyme adsorbed followed the sequence YBS colloid>kaolin>LS colloid>goethite. The presence of ligands also decreased the binding energy between the enzyme and soil colloids or minerals. With the increase of ligand concentration from 10mmol L-1 to 400m mol L-1 different bchaviors for the adsorption of enzyme were found in the colloid and mineral systems studied. A sharp decrease in enzyme adsorption was observed on goethite while gradual decreases of enzynle adsorption were recorded in the two soil colloid systenls. However, no any decrease was found for the amount of enzyme adsorbed on kaolin at higher ligand concentrations. When phosphate or citrate was introduced to the system before the addition of enzyme, the ligarl (Is usually enhanced the adsorption of enzyme. The results obtained in tills study suggested the important role of kaolinite mineral in the adsorption of enzyme molecules in acidic soils in the presnce of various ligands.