To improve the thermal properties and mechanical properties of synthetic biodegradable polymers, poly(butylene succinate) (PBS) and poly(hexamethylene isophthalamide-co-terephthalamide) (PA6IcoT) are reactively blended in a LIST corotating processor under melting conditions. The products are fractionated into insoluble and soluble parts using chloroform as the solvent. The Fourier transform infrared spectra of these two fractions confirm that the exchange reaction between PA6IcoT and PBS occurs when p-toluenesulfonic acid is used as the catalyst. On the basis of the C-13 NMR analysis, the pathway of the exchange reaction is described. The extent of exchange reaction, average length of the various sequences, and degree of randomness in the reactive blends are calculated. It has been found that the randomness of copolymers is increased with the increase in reaction extent. Scanning electron microscopy (SEM) is employed to investigate morphology development of the reactive blends. It shows that the copolymers generated by the exchange reaction act as the compatibilizer to improve the compatibility of PBS and PA6IcoT. The fraction of PA6IcoT- and PBS-rich phases is significantly reduced with increasing reaction extent.