The effects of HgCl₂ concentration of 0, 10, 100, 1000 and 10,000 μmol/L on the submicrostructure of peanut seedling stems and leaves of were observed under transmission electron microscope. The results showed that when the HgCl₂concentration was 10 μmol/L, the organelles of stems and leaves were not affected. When the HgCl₂ concentration was 100 μmol/L, the cell nucleus, chloroplast and mitochondria of stems and leaves began to appear membrane damage. When the HgCl₂ concentration was 1,000 μmol/L and 10,000 μmol/L, the membrane structure of stems and leaves cells of peanut seedling was seriously damaged, and the mitochondria and chloroplast were damaged. With the increase of mercury concentration, the organelles in stems and leaves cells of peanut seedlings showed obvious damage, but the tolerance was slightly different.