This paper reports the accumulative mechanism of elements assimilated by plants in the Xiaoxilin Pb-Zn deposit of Heilongjiang and Jiaolongzhang of Gansu. Studies show that there exist marked difference between accumulative mechanism of nutritive elements and that of toxic elements. When the nutritive elements are assimilated by plant, they are accumulated in every organ, and the organs are related to the function of elements in plants.Toxic elements are excluded when they are assimilated by plant they are accumulated in organs, where organ toxic elements exert very little or no poisonous effect upon plants.