Crystallization kinetics, thermal and mechanical properties of polyester(PCC) based poly(tetramethylene glycol) copolymer(PCCP) and blends(PCC/PTMG) were investigated by using differential scanning calorimetry(DSC), polarized optical microscopy(POM) and tensile tester. This study focused on the effect of soft segment on thermal and mechanical properties. The PCC showed significant cold crystallization at 115℃ and spherulite structure. Whereas no cold-crystallization peak appeared in the all PCCPs except PCCP5wt%. Moreover, tensile modulus and strength slightly decreased dependent on PTMG content. This can be explained by the existence of the interaction between PCC and PTMG molecular chains, which blocks the movement of the chain segments of PCC at this temperature. Compared to the PCC/PTMGs, PCCPs were largely affected by PTMG on thermal property, especially melting energy. In contrast, both tensile modulus values showed similar behaviors, indicating that the content of PTMG affects on rigidity regardless of molecular structure.