Abstract: The crystallization behaviors of homo-polypropylene and random co-polypropylene with and without nucleating agent were investigated comparatively by using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WXD), and polarized optical microscopy (POM). The experimental results indicated that the faster the cooling rate of melted polypropylene was, the greater the content of β-polypropylene was, which was more obvious for homo-polypropylene than for random co-polypropylene. Meanwhile, it was found that homo-polypropylene with lower melting flow rate was more likely to form β-form crystallites. In the presence of β-nucleating agent, both homo-polypropylene and random co-polypropylene possessed greater number of spherulites, higher crystallization temperature, crystallization activation energy, the content of β-polypropylene and crystallinily, when compared with their pure counterparts. However, the influence of cooling rates on the content of β-polypropylene was reduced for both homo-polypropylene and random co-polypropylene after nucleating agents being added. Under the same circumstances of cooling rates of melt and content of β-nucleating agent, the homo-polypropylene always had higher crystallinity and content of β-polypropylene than the random co-polypropylene.