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HfB2 powders were prepared successfully by combining sol-gel with carbonthermal reduction. The phase components and micro-structure were analyzed by XRD and SEM, respectively. The oxidation behavior of the powders at high temperature was measured by TGA. The results show that reduction temperature and content of boric acid have obvious effects on the purity, the average size and the oxidation behavior of HfB2. As the temperature is 1800 ℃ and the content of boric acid is higher than its stoichiometric ratio of the synthesizing of HfB2, the obtained HfB2 with high purity and uniform particle size has the better oxidation behavior. Moreover, the reactive mechanism of preparing HfB2 powders was also discussed