Beryllium oxide has such characteristics as high melting point, high hardness, low dielectric constant and good thermal conductivity, and is widely used in nuclear technology, vacuum electronics and special metallurgy. Beryllium hydroxide obtained by sulfuric acid process is used as the object, beryllium oxide is prepared by roasting, and the decomposition law of beryllium hydroxide is studied. The results show that: 1) the volatilization of adsorption water and crystal water mainly occurs during the preheating process, and the longer the preheating time, the higher the temperature, the more water volatilizes, and the smoother the surface of Be(OH)₂ particles, but when the preheating temperature is too high, the particles will be partially broken; 2) Be(OH)₂ decomposition mainly occurs during the roasting process to form BeO, and the longer the roasting time, the higher the temperature, the greater the degree of decomposition, and the more serious the particle breakage; 3) under the conditions of 500 ℃ and 3 h for preheating temperature and time, and 1 000 ℃ and 3 h for roasting temperature and time, respectively, the optimal Be(OH)₂ decomposition results are achieved, and the weight loss rate of the roasted products reaches 60.1%. The results can provide a certain reference for the industrial production of beryllium oxide by beryllium hydroxide roasting.