This article summarizes recent progress in research on oxidation behavior of pack-cemented Mo-9Si-18B alloys with a Mo5SiB2/MO two-phase eutectic microstructure. The deposited layer of as-cemented Mo-9Si-18B alloy consists Of MoSi2. Upon heating to temperatures above 1500degreesC, the deposited layer is transformed into B-doped Mo5Si3 through a reaction between the deposited layer and the matrix containing B. Steady-state oxidation is observed at 1300-1500degreesC and its rates are almost equal to those Of MoSi2. No significant increase in weight loss was observed in a short-term cyclic oxidation test, since the columnar structure with orientation preference in B-doped Mo5Si3 coating layer must be reduced thermal stress in the cyclic oxidation test.