According to the Mannich-Reaction, a kind of chelating hydrogel grafted with dithizone was prepared from polyacrylam (PAM), formaldehyde and dithizone. And the optimum adsorption condition of disposing Pb (II) from aqueous solution was studied. The result indicated that at 30℃, pH=6-7,0.5g of the chelating hydrogel grafted with dithizone processed 10mg/L 100mL Pb (II) solution for 2h, and then 99.5% of Pb (II) was removed.