To investigate the effects of chain structures, such as the number of methylene groups and different aromatic units in polyesters, on the ester interchange reaction during melt blending, PCL was blended with PET, PTT, PBT of PEN. The ester interchange reaction of blends was characterized by $^{1}H$-NMR and the thermal property, crystal structure and morphology of blends were studied by DSC, X-ray and SEM analyses. The ester interchange reactions could be confirmed in PET/PCL and PTT/PCL blends, but did not occur significantly in PBT/PCL and PEN/PCL blends. At the higher degree of ester interchange reaction, melting temperature of blends decreased and the morphology of blends changed to a homogeneous phase. It appears that ester interchange reaction during melt blending is affected by the chain structure of polyester as well as the concentration of terminal alcohol, carboxyl and ester groups.