A method for preparing propylene polymer of high melt strength using direct polymerization method is provided, which comprises in different propylene polymerization reaction stages operated in series, according to the requirements of different molecular weight fraction, producing propylene polymer having broad molecular weight distribution and containing "very high molecular weight fraction" by controlling the kind and the ratio of external electron donor component of Ziegler-Natta catalyst system in different reaction stages. The polymer has very good mechanical properties, especially has very high melt strength. A propylene homopolymer having high melt strength is also provided, which has the characteristics of: (1) a MFR of 0.2-10g/10min at 230?, a load of 2.16kg; (2) a molecular weight distribution Mw/Mn=6-20; (3) a content of fraction having molecular weight of greater than 5 million of greater than or equal to 0.8wt%; (4) Mz+1/Mn of greater than or equal to 70. The homopolymer can be used for preparing foamed articles, thermoforming articles, biaxially stretching films, blow-molded films and blow-molded articles.