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This paper aims to improve the oxidation resistance of MoNbTaVW (at%) refractory high-entropy alloys after flame tests at 1350 ℃ with Si/Al pack cementation coatings. After the Si/Al pack cementation coatings were applied, a coating layer of about 80 μm with a sequence of Si-rich layer (silicide)/interdiffusion layer/Al-rich layer (aluminide)/Al diffusion layer was formed. After the flame tests at 1350 °C for 20 min, the uncoated specimens formed composite oxides of Nb 2 O 5 (s), Ta 2 O 5 (s), and V 2 O 5 (s) with porosity of MoO 3 (g) and WO 3 (g) with a weight gain. On the other hand, the Si/Al coated specimens were composed of Si-rich layer (silicide)/ interdiffusion layer/Al-rich layer (aluminide)/Al diffusion layer. After the flame tests, SiO 2 and Al 2 O 3 ceramic protective layers were formed on the surface and prevented additional oxidation. The oxidation behaviors of MoNbTaVW alloys and the Si/Al pack cementation coated alloys were discussed with microstructures and phase development.