Isotactic polypropylene (iPP) and N, N’-bis(benzoyl) sebacic acid dihydrazide (TMC-300) blends were prepared by means of melt blending. The effects of TMC-300 on the crystallization and melting behaviors, crystal structure and mechanical properties of iPP were studies by DSC, XRD, SEM, POM and mechanical test. The results showed that the addition of TMC-300 had a significant nucleation effect on iPP. When the weight fraction (w) of TMC-300 was 0.6%, the crystallization temperature of iPP increased from 117.2℃ to 126.9℃, and the nucleation efficiency reached up to 56.3%. Pure iPP exhibited a half-time of crystallization (t1/2) of 4.85 min when isothermally crystallized at 130℃, however when w(TMC-300) was 0.2%, the value of t1/2 became 0.52 min and decreased by nearly 89%, indicating that the crystallization rate of iPP increased rapidly after adding TMC-300. Meanwhile, the crystal structure of iPP did not change with the incorporation of TMC-300. Moreover, the impact fracture surface of iPP with addition of TMC-300 showed obvious characteristics of multi fold ductile fracture. When w(TMC-300) was 0.2%, the elongation at break of the composites increased from 674.8% to 833.2% and the notched impact strength increased from 32.5 J/m to 43.2 J/m, which indicated that the addition of TMC-300 could effectively improve the toughness and plasticity of iPP. Finally, the effects of TMC-300 on the crystallization and mechanical properties of iPP were compared with that of nucleating agent TMC-328 and HPN-68L. When w(TMC-300) was 0.2%, the crystallization temperature was 126.2℃, which was slightly higher than that of 0.2% TMC-328 (125.2℃), and the notched impact strength (43.2 J/m) was 15.8% higher than that of 0.2% HPN-68L (37.3 J/m).