The influence of the polymerization time on the molecular weight (M-w, M-n, M-p, and M-z), molecular weight distribution (MWD) and relative MWD of polypropylene (PP) in the propylene polymerization with a Mg(OEt)(2)/DIBP/TiCl4/PTES/AlEt3 Catalyst system in the slurry phase has been studied by using gel permeation chromatography (GPC), where Mg(OEt)(2), DIBP (diisobutyl phthalate), TiCl, PTES (phenyl triethoxy silane), and tri-ethyl aluminum (TEA) are support, internal donor, catalyst, external donor, and cocatalyst, respectively. It has been found that the increase of the polymerization time increases the molecular weight and MWD of PP. (c) 2006 Wiley Periodicals, Inc.