In this article, the influence of rosin-type nucleating agent (Nu-Na) and low density polyethylene (LDPE) on the crystallization process of polypropylene (PP) from the melt state was studied by differential scanning calorimeter and polarization microscope. It was found that LDPE obstructed the crystallization of PP, decreased the crystallization rate of PP. The rosin-type nucleating agent Nu-Na substantially improved the rate of crystallization, and decreased the size of spherulites also. The cooperative effect of LDPE and Nu-Na made the crystallization rate of PP increase greatly, the spherulites of PP became much smaller and dispersed more uniformly, and the transparency of PP was further improved evidently. The crystallization temperature (T-c) and melting temperature (T-m) of PP and LDPE in PP/LDPE/Nu-Na (97:3:0.5) were not affected by the number of mixed passes-the nuclei migration from PP to PE had not happened in the mixed passes. (C) 2003 Wiley Periodicals, Inc.