Abstract: This is an article in the field of metallurgical engineering. High purity hafnium diboride (HfB₂) powders were synthesized from hafnium oxide (HfO₂) and boron carbide (B₄C) powders via sodium chloride as the molten salt through boron/carbon thermal reduction. Investigations were carried out to determine the effect of synthesis parameters (reaction temperature, holding time) and boron content on the phase composition and microstructure of the synthesized hafnium diboride powders. The results demonstrated when sodium chloride was used as the molten salt medium, the conversion of HfO₂ to HfB₂ started at 1300 ℃, which was significantly lower than the temperature required for conventional hafnium diboride. The purity of the HfB₂ powder was the highest when the boron excess was 20%, with the reaction temperature and holding time being 1400 ℃ and 2 h, respectively. HfB₂ crystalline peaks were prominent in X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed HfB₂ in a densely agglomerated structure.