Effects synthetic aluminum oeides (gibbsite) on positive,negative charges,and zero point of net charges (ZPNC) in five soils from southern China were studied by way of coating.After roaring with aluminum oxides,positive charges of these soils increased to varying degrees.But the increments reduced with the increase of pH value.When pH value was about 7,positive charges of four soils approched to zero,but there were still a few positive charges in the latosol.