The influence of the main-chain liquid Introduced crystalline polyester (PBDPS) on the crystallization and melting behaviors of isotactic polypropylene (iPP) has been investigated by differential scanning calorimetry (DSC), X-ray diffraction (WAXD), and polarized optical microscopy (POM). The results suggested that PBDPS is an efficient beta-nucleating agent for iPP. The melting crystallization temperature as well as beta-crystal of iPP increased with increasing of PBDPS content. The relative content of beta-iPP crystals (k(beta)) can reach 96.6% while adding 4% PBDPS during isothermal crystallization at 135 degrees C. The increased beta-nucleation efficiency was ascribed to the adjacent phenyl rings in side groups of PBDPS stacked well together even when the temperature was higher than its clearing point (T-i). Moreover, the distance between stacked phenyls is 0.32 nm, which is half of the unit cell parameter in the c-direction of beta-iPP, indicating a lattice match between beta-iPP and PBDPS.