In this work,the syntheses of new thermally stable poly(amide-imide)s with pendant 2-pyridyl-1,3,4-oxadiazole units in n-butyl methyl imidazolium bromide as reaction media have been reported.A new dicarboxylic acid has been derived from the reaction of diamine,2-(5-(3,5-diaminophenyl)-1,3,4-oxadiazole-2-yl)pyridine(POBD),and trimellitic acid anhydride.Polymers were prepared from the reaction of the diimide-diacid(DIDA) and different aromatic diamines in butyl methyl imidazolium bromide,[bmim][Br],in the presence of triphenyl phosphite(TPP) as condensing agent without needing any extra components.The prepared poly(amide-imide)s were characterized by FTIR,elemental analysis,and through the synthesis of a model compound.The prepared polymers were soluble in polar and aprotic solvents,such as DMF,DMSO, NMP and DMAc.The inherent viscosity of the polymer solutions was in the range of 0.52-1.33 dL/g measured in concentrated H_2SO_4 at a concentration of 0.125 g/dL at(25±0.5)℃.The results are compared with the results obtained from common direct polycondensation with NMP as solvent.Polymers obtained in ionic liquid showed higher inherent viscosity than that of polymers obtained via classical method in NMP.Thermal properties of the polymers were studied with DSC and TGA methods. In this work, the syntheses of new thermally stable poly (amide-imide) s with pendant 2-pyridyl-1,3,4-oxadiazole units in n-butyl methyl imidazolium bromide as reaction media have been reported. A new dicarboxylic acid has was derived from the reaction of diamine, 2- (5- (3,5-diaminophenyl) -1,3,4-oxadiazole-2-yl) pyridine (POBD), and trimellitic acid anhydride. the diimide-diacid (DIDA) and different aromatic diamines in butyl methyl imidazolium bromide, [bmim] [Br], in the presence of triphenyl phosphite (TPP) as condensing agent without needing any extra components. prepared poly (amide- imide) s were characterized by FTIR, elemental analysis, and through the synthesis of a model compound. The prepared polymers were soluble in polar and aprotic solvents, such as DMF, DMSO, NMP and DMAc. The inherent viscosity of the polymer solutions was in the range of 0.52-1.33 dL / g measured in concentrated H 2 SO 4 at a concentration of 0.125 g / dL at (25 ± 0.5) ° C. The results a re compared with the results obtained from common direct polycondensation with NMP as solvent. Polymers obtained in ionic liquid showed higher inherent viscosity than that of polymers obtained via classical method in NMP. Thermo properties of the polymers were studied with DSC and TGA methods.