In this study, modified polyethersulfone (PES) membrane with pH sensitivity and heavy metal ion adsorption was prepared by blending a copolymer of poly(acrylonitrile-co-maleic anhydride) (P(AN-MA)). The copolymer was synthesized by free radical reaction using deionized water as the solvent, and was characterized by Fourier transform infrared spectroscopy (FTIR) analysis, elemental analysis, and gel permeation chromatography technique (GPC) measurement. Scanning electron microscopy (SEM) was used to investigate the morphology of the membrane. The modified PES membranes showed excellent pH sensitivity and pH reversibility. Furthermore, the modified PES membrane had the ability to absorb Ag+, Cu2+, Fe2+, and Fe3+. In addition, three simplified kinetic models (pseudo-first-order, pseudo-second-order, and intraparticle diffusion model) and adsorption isotherms (Langmuir and Freundlich) were used for the analysis of Cu2+ adsorption.