An aromatic diamine monomer, N,N'-bis (p-aminophenyl) terephthalamide (PTP) was synthesized by employing sodium hydride as catalyst, 1,4-phenyleneamine (PDA) and dimethyl terephthalate (DMT) as starting materials. The structure of monomer was characterized by FT-IR, H-1-NMR and elemental analysis. A series of new poly(amide-imide)s (PAIs) having inherent viscosities of 1.85-2.07 dL/g were synthesized from aromatic diamine PTP with various commercially available aromatic dianhydrides using a standard two-stage process with thermal imidization of poly(amic-acid) (PAA) films. The structure of polymers was respectively investigated by FT-IR. The WAXD patterns indicated an amorphous morphological structure of these polymers. All the new PAIs had good thermal stability with the glass transition temperature of 234-248 degrees C, the temperatures of 5% and 10% weight loss in nitrogen were in the range of 518-541 degrees C and 543-564 degrees C respectively. All PAIs were found to hold outstanding mechanical properties with the tensile strengths of 267.83-326.14 Mpa and Young's modulus of 4.67-5.83 GPa.