Adsorption of acid phosphatase on yellow brown soil, latosol, kaolinite, goethite and δ-MnO₂ in a series of phosphate solutions different in concentration was investigated.Results showed that, with increase in phosphate concentration, isotherms of phosphatase adsorption on soil colloids and minerals were changing from L type (Langmuir) to C type (linear).The transformation of adsorpt ion isotherm was ascribed to competition between phosphate and enzyme molecules for adsorption sites on soil colloids and minerals.With the increase in phosphate in the system from 0 to 100 mmol L^-1, a sharp fall was observed for the amount of enzyme adsorbed.When the concentration came within the range of 100~500 mmol L^-1, no remarkable variation of the amount of enzyme adsorbed was observed.The inhibitory effect of phosphate on the adsorption of enzyme was dependent on the surface characteristics of soil colloids and minerals, especially the quant ity of hydroxyls, the concentrat ion of phosphate and the amount of enzyme added.The most effect was found in goethite and lateritic colloids which contain more ferri-aluminum hydroxide.