In this paper, β-phase isotactic polypropylene (β-iPP) was prepared with two different β nucleating agents (NT-A and NT-D). The melting and crystallization behavior, crystal morphology and mechanical properties of β-iPP were studied by means of DSC, WAXD, PLM and mechanical tests. It is found that the spherulites become smaller, and tensile strength, tensile strain at break and notched impact strength increase for the nucleated iPP. NT-D is more efficient than NT-A. The notched impact strength is three times greater than that of pure iPP for the samples nucleated by NT-D. The injection molded specimens have obvious skin-core structures.