A method for preparing composite sulfur-modified powdered activated carbon includes the following steps: providing a powdered activated carbon; proceeding a drying step on the powdered activated carbon; proceeding a liquid-phase sulfur modification step on the dried powdered activated carbon; proceeding a granulation step, so as to obtain a granular powdered activated carbon from the sulfur-modified powdered activated carbon; and proceeding a vapor-phase elemental sulfur heating step on the granular powdered activated carbon, so as to form the composite sulfur-modified powdered activated carbon.