A high-temperature oxidation-protective Si-Mo coating on a molybdenum alloy substrate was prepared by slurry sintering method. The structure, composition, phase distribution, and oxidation behavior of the coating were studied. The results show that the coating has a double-layer microstructure with an outer MoSi2 layer and an inner Mo5Si3 layer. After oxidation, the coating is composed of a SiO2 outer layer, a MoSi2 middle layer, and a Mo5Si3 inner layer. The mechanism of the phase distribution and the oxidation kinetic equation were also studied. The oxidation rate Kp determined over 12h at 1650°C, was found to be 0.061mg2cm−4h−1. The excellent oxidation protective ability of the coating at ultra-high temperatures is attributable to the formation of self-healing SiO2 on the coating surface after the oxidation of MoSi2.