Abstract: A series of polyimide materials were successfully prepared by embedding o-carborane cage structure into polyimide main chains. First, the diamine monomer (DNCB) containing o-carborane unit was designed and synthesized, and then copolymerized with 4,4'-diaminodiphenyl ether (ODA) and 3,3',4,4'-benzophenone tetracarboxylic anhydride (BTDA) to synthesize the polyamic acid (PAA) precursor solution. PAA films were prepared by solution casting method, and then polyimide films containing different contents of carborane unit were obtained after high-temperature thermal imidization. Thermogravimetric analysis (TGA) shows that the addition of DNCB significantly improves the thermal stability and thermal oxidation stability of polyimide materials. When the molar content of DNCB in all diamines reaches 40%, the temperature corresponding to 5wt% mass loss (T_5%) increases by nearly 13℃, T_10% increases by nearly 43℃ and the mass residual rate was as high as 82.6wt%. Under the air atmosphere, T_5% increases by nearly 36℃, T_10% increases by nearly 64℃, and the mass residual rate reaches as high as 83.1wt%. This is due to the oxidation of carborane cage and the formation of multi-layer passivation protective layer on the surface of the film, which prevents the degradation of internal polymer materials in contact with oxygen.