The invention relates to a forming mold for forming high-density steel sleeve and a forming method. The steel sleeve forming mold is characterized in that the mold cavity has a thin lower wall and a thick upper wall; chill iron is arranged outside the walls of the mold cavity stepwise; molten copper is cast into the mold cavity slowly through a cap of the steel sleeve forming mold; the heat generated by the molten copper in the lower section of the mold cavity is absorbed rapidly by the chill iron outside the mold cavity walls, and simultaneously a shrinkage generated in the solidification process of the molten copper chilled by the chill iron is compensated immediately by molten copper continuously cast in the mold cavity. Accordingly, the copper sleeve can be formed sequentially by casting, chilling, shrinking, compensating, casting, chilling, shrinking, compensating, and so forth, and then the cap is removed to obtain the final product. The forming mold has the advantages that the molded copper sleeve has high density, high seismic resistance and long service life, and that the production efficiency is greatly improved.