U-Polymer, a kind of polyarylate, was synthesized by interfacial polycondensation method with terephthaloyl chloride (TPC), isophthaloyl chloride (IPC), and bisphenol A (BPA) as raw materials. The structure of the U-Polymer was characterized by IR and H-1-NMR spectra. Then, an amorphous poly(ethylene terephthalate) (APET) was prepared with the introduction of the U-Polymer to the PET sequence to improve thermal and mechanical behaviors of PET via the polymerization process. The structure and property of the APET were characterized by DSC and DMA. The results showed that the APET exhibits amorphism, transparency, higher glass-transition temperature (T-g), and higher storage modulus than that of PET.