In this paper, the directional emissivity of Ti-6Al-4V alloy at 0°--84° was measured using Fourier transform infrared spectroscopy at a temperature range of 573--953 K and a wavelength range of 3--20 μm. The influence of direction on the spectral emissivity was systematically studied. Results show that the emissivity of Ti-6Al-4V alloy is similar to that of an insulator in the angle range of 0°--84° when the measurement wavelength is less than 10.3 μm, and therefore, it is more similar to that of metal when the wavelength exceeds 10.3 μm. The emissivity increases with temperature that ranges between 573--773 K, and it is observed that the change trend of emissivity with wavelength is opposite for the angle range of 0°--70° and 80°--84°. When the Ti-6Al-4V alloy is oxidized, its emissivity is maximum at 60°, and the non-metallic properties of emissivity at long-wavelength are evident with the increasing oxidation time. Therefore, this study enriches the directional spectral emissivity database of Ti-6Al-4V alloys and provides data support for radiation temperature measurement technology.