In order to improve the Cd2+ adsorption ability, the granular activated carbon (GAC) was modified with different treatments, and the Cd2+ removal efficiencies (REs) by the treated GACs were then comparatively investigated under different conditions. The surface physical-chemical properties of these carbons were further characterized in virtue of BET and Boehm’s titration, etc. The results demonstrate that the specific surface area and surface oxy acidity functional groups of GAC changed to some certain after the different treatments, especially for that with HNO3 oxidizing. It therefore led to an improvement of Cd2+ adsorption ability, and the corresponding REs by the N-GACs that were respectively modified with 10% and 70% HNO3 were significantly higher than that by the original GAC (i.e., 41% and 57% vs. 10%). pH was found to be the most vital influencing factor for the Cd2+ adsorption, and the Cd2+ REs by the tested GACs were all increased with an elevation in the pH value.