Abstract: The bentonite of Shangtianti district belongs to Ca-bentonite. Its major mineral is Ca-montmorillonite; its colloidal dispersion is not go od; its cation exchange capacity is low; and its exchangeable cations are Ca 2+ and Mg2+. The studies on crystallochemical structure of montmorilloni te indicates that the montmorillonite has a higer ordering degree and a larger l ayer charge. The crystallochemical data indicate that the Shangtianti bentonite is suitable for preparing the activated white clay. The influence of acid curin g, solid-liquid ratios, activation time on the products properties were analyse d. The optium technoloqical conditions were obtained.At the beginning the pur ification of ore was made by pounding of raw ore to the serous liquid. Later on the ore was activated by 16%～20% sulfuric acid solution. The activat ion time was 6～8 hours. The solid-liquid ratio was 1:2. The decolouring forc e of the activated white clay was 156～218 and its activity degree was above 222 m.mol/100g. The main quality parameters of the white clay reach or outstrip the required trade standards. The decolourization effect was very good.