Based on the study of W-Y2O3 metallization process of Al2O3 (including 95% Al2O3 ceramic and Al2O3 single crystal), the high-temperature brazing joints of single crystal Al2O3/Pd/Nb were fabricated. W-Y2O3 metallization mechanism of Al2O3 and Pd brazing mechanism of Al2O3/Nb were analyzed. The results show that there was aggregation behavior of Y near the interface between the Al2O3 substrate and metallizing layer; meanwhile Al content decreased. This resulted from the diffusion of some new solid phase products at the interface of ceramic/metallizing layer during metallization. The diffusion direction was mainly towards the metallizing layer. The W and Nb elements nearly diffused into the whole Pd brazing interlayer during high-temperature brazing, which led to forming of brittle solid solutions or intermetallic compounds in the solder layer and near Nb/Pd interface, resulting in micro-cracks.