Adsorption of phosphate by different types of soils with variable charge and the changes of negative and positive charges of soil after phosphate adsorption as well as the effect of pH and free iron oxides on the changes of soils were studied. The resalts showed that phosphate was all adsorbed by soils when a smaller amount phosphate was added, and the amount of phosphate adsorbed accounted for 40-85% of phophate added. Phosphate adsorption by soils was closely related with free iron oxides in soils.The positive charge decreased but negative charge increased after phosphate adsorption by soils. The increment and decrement of charges were larger at lower phosphate adsorption. The charges of soils have a parabola relation with phosphate adsorbed. The contribution of phosphate adsorbed to net negative charge of soils ranged between 0.3-1.0 mole per mole phosphate, being the smallest in latosol and the largest in yellow soil.The increment of negative charge of latosol after phosphate adsorption was lower at low pH, but increased with pH increase. For red soil and yellow soil, increment of negative charge after phosphate adsorption was not affected obviously by pH value, The free iron oxides in soils caused a decreased contribution of phosphate adsorbed to negative charge of soils.