Environmental Barrier Coatings (EBCs) can prevent SiC-based ceramic matrix composites from corrosion at high temperatures. However, the low melting point of conventional Si bond layers limits the operating temperature of EBCs to 1350 °C. Herein, a MoSi2-HfO2 duplex bond coat was designed and showed robust adhesion on SiC substrate after corrosion at 1450 °C for 100 h in steam/oxygen atmosphere. A mixed oxide layer was observed to in-situ form at the interface between the MoSi2 and HfO2 layers, containing SiO2, Hf-Si-O glass and HfSiO4. This oxide layer was proven to effectively inhibit further oxidation/corrosion of the coating and the substrate. The phase composition evolution and anti-oxidation mechanism were systematically analyzed.