The carboxymethyl starch was prepared by dry method using the cassava starch, mechanically activated for 60 min, as a starting material. The static adsorption behavior of the carboxymethyl starch , the adsorption thermodynamics and kinetics of the the carboxymethyl starch on Cu（Ⅱ）were investigated, meanwhile the product was characterized and the adsorption mechanism was stutied. The results show that the adsorption characteristic of carboxymethyl starcht on Cu（Ⅱ） is adapted to Freundlich and Langmuir adsorption isotherm equation. The adsorption thermodynamic parameters including enthalpy change △H, free energy △G change and entropy change △S were all negatived under the temperituer of 303K, 313K and 323K. The adsorption of the Cu（Ⅱ） on the carboxymethyl starch was an intraparticle diffusion process, and the adsorption mechanism including physical adsorption, ion-exchange and coordination.