Abstract: With o-phthalic acid and aluminium isopropoxide as raw materials, a new salt of phthalic acid hydroxy aluminium was prepared, which was used as a nucleating agent for isotactic polypropylenes (iPP) and was denoted as OXA. Thermal stability of OXA was characterized by using thermogravimetric analysis technology (TG). The influence of OXA on the crystal form, crystalline morphology, and crystallization behavior of iPP were investigated using X-ray diffraction, polarized light microscopy, and differential scanning calorimetry. When the content of OXA was 0.3 wt%, the crystallization temperature (Tc) was 13.26 ℃. In addition, OXA increased the degree of crystallinity from 52.49 % to 58.37 % and refined spherulites were observed. The flexural strength was increased from 46.19 to 50.89 MPa.