Microstructures and oxidation behaviors of four Dy-doped Nb-Si-based alloys at 1250°C were investigated. The nominal compositions of the four alloys are Nb-15Si-24Ti-4Cr-2Al-2Hf-xDy (at.%), where x = 0, 0.05, 0.10 and 0.15, respectively. Results showed that the four alloys all consisted of Nbss, aNb 5 Si 3 and cNb 5 Si 3 , and the addition of Dy produced no obvious effect on the phase constitution and the microstructures of Nb-Si-based alloys. After oxidation at 1250°C for 58 h, it was found that the addition of Dy accelerated the oxidation rate of Nb-Si-based alloys and caused a larger weight gain, accompanied by the formation of a more porous and less protective oxide scale. The oxides of Nb 2 O 5 , Ti 2 Nb 10 O 29 , TiNb 2 O 7 , Ti 0.4 Cr 0.3 Nb 0.3 O 2 and glassy SiO 2 were formed on Dy-doped Nb-Si-based alloys. The hightemperature oxidation mechanism of Dy-doped Nb-Si-based alloys was discussed.