A considerable amount of research has been conducted domestically and internationally on the theory and process of preparing metallurgical grade aluminum hydroxide through the decomposition of sodium aluminate solution, and many research results have been achieved, promoting technological progress in the alumina industry. However, existing research on the decomposition process of sodium aluminate solution mainly focuses on the production process of metallurgical grade aluminum hydroxide, and there is less research on the process of preparing ultrafine aluminum hydroxide through the decomposition of sodium aluminate solution. Compared with the production process of metallurgical grade aluminum hydroxide, the preparation process of ultrafine aluminum hydroxide has certain differences in temperature system, seed quality, seed rate, decomposition time, and crystal growth mechanism. At present, the main method used in China is the two-stage seed separation method of sodium aluminate solution to prepare ultrafine aluminum hydroxide, which has a long process flow and complex production process. In order to simplify the production process, this chapter adopts a one-step process to prepare ultrafine aluminum hydroxide, and studies the influence of relevant factors on the decomposition rate and particle size of sodium aluminate solution decomposition to prepare ultrafine aluminum hydroxide. To optimize production processes and improve product performance.