A copolymers are important compounds today because of their wide applications in various industrial and medical fields and in other fields. Therefore, the study of preparing many of these polymers has been studied. This research involved preparing linear polyester contain Schiff-base unit by interfacial polycondensation three type diacid chloride (Succinoyl Chloride, Adipoyl Chloride and sebacoyl Chloride) in a chloroform /water system employing phase transfer catalyst with monomer containing two hydroxyl which is derived from a 4-hydroxy aniline reacted with a 4-hydroxy benzaldehyde monomer. The monomer (EM1) and polyester (EM2, EM3, and EM4) were characterized by FTIR, 1H NMR, 13C NMR and TGA analysis. The polyester–Schiff base so obtained show good thermal stability.