In this work, octamethylenedicarboxylic dibenzoylhydrazide (TMC-300) was used as a highly efficient α-phase nucleating agent for isotactic polypropylene (iPP) for the first time. The influences of TMC-300 on crystallization and melting behaviors as well as mechanical and thermal properties of iPP were analyzed by differential scanning calorimeter, polarizing optical microscope, wide-angle X-ray diffractometer, and universal mechanical tests. The results reflected that TMC-300 had excellent nucleation effect and that 0.20 wt% was the optimal ad...