Abstract: Acid value of the active carbon (AC) on catalytic carbonization of PP/NiO/AC was investigated by modified coconut shell activated carbon through HNO₃ oxidation. The effects of acidification temperature, time and concentration on the acid value were studied. Specific surface area and pore structures of the AC were characterized by BET and SEM. The type and content of surface oxygenic functional groups was characterized by Beohm titration and XPS. The results indicated that specific surface area and pore structure were changed when AC was treated by HNO₃. The surface oxygen groups increased significantly, mainly including -COOH, -CO and -OH. The increase of surface oxygen groups of AC promoted the carbonization ability of polypropylene, and improved the structure of carbon residue.