In order to improve the absorption ability of Cd 2+, the activated carbon is modified by HNO3. Additionally, the structure changes of activated carbon with and without treatment are studied in virtue of BET, Boehm and other instruments. The research demonstrates that the specific surface area and the number of activated carbon surface functional groups dramatically change after treatment, and the specific surface area and the figure of acid functional groups after HNO3 oxidizing increase. It is worth mentioning that under the condition of pH with 7.00, the removal rate of Cd 2+ by raw activated carbon is approximately 10%, in contrast, the removal efficiency reached 41% by 10% N-GAC and 57% by 70% N-GAC, the removal effects of Cd 2+ could be improved after modification. With the dosing quantity of modified activated carbon increased, the removal effects of Cd 2+ are also increased. PH is the biggest influence factor of removing Cd 2+. As the pH of solution increases, the removal rates of three kinds of adsorbent for Cd 2+ increases. Adsorption kinetic research shows that the adsorption reaction of Cd 2+ on 10% N-GAC is suitable to Lagergren pseudo-first-order (PFO) reaction in the former 20 min and more suitable to Lagergren pseudo-second-order (PSO) reaction after 20 min.