In this work, amidoxime-modified polymer containing imidazolinyl (AM/AO/NIPA) was synthesized by acrylamide (AM), acrylonitrile (AN) and 1-(2-N-allyl ammonia ethyl)-2-oleic acid imidazole (NIPA). Then, the copolymer was characterized by FT-IR, FE-SEM and TG. By the static adsorption experiment, the adsorption capacity of Cu2+ by AM/AO/NIPA was investigated and was compared with typical adsorbent polyacrylamide (PAM); also, equilibrium kinetics and isotherms were obtained and further discussed adsorption mechanism. The results showed that the Cu2+ adsorption capacity of AM/AO/NIPA was seldom effected by the pH of the weak solution. The Cu2+ adsorption to AM/AO/NIPA reached equilibrium at 30 ℃ after 3 h, the pH of original solution is 5 and initial concentration is 100 mg/L; and the adsorption capacity is 37.32 mg/g at that time. The whole adsorption process is subject to the pseudo-second-order model, which is dominated by chemical adsorption. The experimental data of the adsorption of Cu2+ by AM/AO/NIPA can be fitted well by both Langmuir and Freundlich isotherm models. Moreover, the maximum adsorption capacity of Cu2+ by AM/AO/NIPA was 267.38 mg/g, three times higher than PAM, which is calculated by fitting Langmuir isotherm models. Furthermore, the amidoxime polymer AM/AO/NIPA remain up to 92.99% of its original adsorption capacity after five circles.