Abstract:With the quickly increasing of demanding in the lithium ion battery diaphragm, boehmite were valuable accordingly. The hydrothermal preparation of boehmite with aluminium hydroxide as precursor is a technical proposal which is easily to be applied in the plant. The influence of reaction conditions, such as slurry solid content, reaction temperature, reaction time and particle size of precursoron conversion rate of boehmite were researched in the article. The results showed that the reaction temperature was the most important influence factor in all tests. The conversion was scarcely occurred when the reaction temperature was less than 180, the conversion were finished more than 45 minutes when the temperature was 200. when the temperature was 220, the conversion was finished in 15 minutes.The original particle of boehmite from hydrothermal preparation was presented in a quadrangular rhombic shape in a submicron scale, the final product was agglomeration of submicrom particles. The research results showed some basic reaction behaviors in hydrothermal preparation boehmite, which can be used to produce boehmite in lithium ion battery diaphragm.