Nb-doped Zr-2[Al(Si)](4)C-5 solid solutions were prepared by in situ hot pressing method and their high-temperature oxidation behavior at 1000 degrees-1300 degrees C were investigated. The oxidation resistance of [Zr-0.9(Nb-0.1)](2)[Al(Si)](4)C-5 solid solutions is improved remarkably compared with Zr-2[Al(Si)](4)C-5 without dopant. The improved oxidation resistance is due to the formation of a more protective oxide scale consisting of (Zr,Nb)O-2, Nb2Zr6O17, Al2O3, and mullite, in which (Zr,Nb)O-2 solid solution is more effective than ZrO2 in depressing the inward diffusion of oxygen. In addition, the decrease of cracks in the oxide scale above 1100 degrees C in Nb-doped sample is also beneficial to the improved oxidation resistance.