Modification of natural polysaccharide polymer to prepare a bioadsorbent for toxic metal is one of the hotspot research on wastewater treatment. The hydrogel (SAH) with three-dimensional structure was fast synthesized under microwave by graft copolymerization of cassava starch and acrylic acid. The SAH was used as an adsorbent of Pb2 , and the effects of microwave power, pH, temperature, contact time and initial Pb2 concentration on the adsorption were investigated. The adsorption mechanism of SAH was studied by the characterization of SEM、FTIR、XPS. It was found that the SAH with macroporous structure could adsorb Pb2 mainly by the formation of a complex with bidentate structures. The SAH with a maximum adsorption capacity of 561 mg/g could be reused. Furthermore, the adsorption of SAH to Pb2 was accurately described by a pseudo-second-order kinetic model and the initial concentration-dependent adsorption isotherm suggested a Langmuir isotherm model.