The invention provides a Pb2+ ion adsorption material in water solution. The Pb2+ ion adsorption material is prepared by adding maleic acid into raw Chinese chestnut inner peel and gamma irradiating the maleic acid and the raw Chinese chestnut. The adsorption ability of the chestnut inner peel for the lead ion is increased by modification of the chestnut inner peel through gamma ray. The adsorption capacity rises to 120mg/g from 85mg/g, thereby providing new materials for treating lead ion pollution in heavy metal sewage by using the adsorption method.