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Refractory high entropy alloys NbMoTaWTi and NbMoTaWZr were prepared by vacuum arc melting.The microstructure and component distribution characteristics were analyzed, and the dynamic behavior during room temperature to 1500℃, as well as the isothermal oxidation behavior at 1200℃ were studied. Results reveal that NbMoTaWTi mainly consists of single body-centred cubic (BCC) phase, and NbMoTaWZr is composed of BCC and Zr-rich phases.These two alloys are both seriously oxidized above 700℃. Comparatively, NbMoTaWTi alloy is superior to NbMoTaWZr in antioxidation below 1300℃.For both two alloys, the oxygen diffusion inward mainly occurs during isothermal oxidation at 1200℃ and catastrophic oxidation takes place after 3 h. The Ti and Zr addition cannot cause selective oxidation. Although these two elements form a composite oxide layer with other refractory metal oxides, the density and the ability to prevent oxidation is not enough.