Abstract: In order to elucidate the adsorption mechanism of the amino methylene phosphonic acid chelating resin (D418) with high efficiency for removal of Cu(II) from wastewater, the influence of pH, ionic strength, contact time and temperature were detailly investigated by adsorption experiment. Meanwhile, adsorption kinetics, adsorption isotherms and site energy distribution theory were used to explain the removal mechanism of Cu(II) on the D418 resin. The results demonstrate that the optimal removal rate of Cu(II) on the D418 resin reaches to 97.20% at the initial pH=9.00, and the change of zeta potential on the influence of removal rate is well compatible with Boltzmann model. Furthermore, the removal efficiency of Cu(II) increases with the ionic strength at the range of 0-0.10 mol/L. According to the comparisons of the linear correlation coefficient values, the data of the adsorption kinetics fits well to the intra-particle diffusion while isotherm model data fits well to the Sips model. Based on the Sips model, the isotherm parameters and the energy distributions of adsorption sites were also conducted, and the result shows that the process of the Cu(II) adsorption on the D418 resin is spontaneous and endothermic. Cu(II) is preferentially adsorbed to the high- energy sites and to the low-energy sites. Based on the XPS and FTIR analysis, the adsorption mechanism of the Cu(II) ions is mainly attributed to the electrostatic interaction, the chemical precipitation and the inner-sphere complexation.