用拜耳法制备高纯氧化铝，将种分得到的高纯三水铝石在不同条件下水热处理脱钠，并对水热产物进行煅烧得高纯氧化铝，分析了水热条件对产物形貌和脱钠效果的影响. 结果表明，水热处理温度约为180℃时，三水铝石[Al(OH)3]转变为一水软铝石(AlOOH)，三水铝石晶间的Na2O返溶于水，且转变过程缓慢，升高温度、降低pH值、延长反应时间均能促进转变过程进行.一水软铝石形貌与三水铝石差异巨大，呈玻璃渣状的四方长条晶型堆叠，更疏松无序. 水热产物于1200℃煅烧后，Na2O含量大幅下降，pH为1时煅烧前Na2O含量为0.0163wt%，煅烧后Na2O含量为0.0187wt%.

High pure alumina was prepared using Bayer liquid. Gibbsite was treated by hydrothermal method under different conditions, then the impurity of sodium re-dissolved in water. Physical and chemical properties of the hydrothermal product were analyzed. The results showed that raising hydrothermal temperature to 180℃, gibbsite changed into boehmite. Na2O returned to dissolution in water during the transformation process of gibbsite, rising temperature and decreasing pH could promote the transformation, prolonging the reaction time could extend reaction, boehmite`s morphology, liking "broken glass" shape, was hugely different from gibbsite after the hydrothermal treatment. Compared with gibbsite, the boehmite was looser and more unordered. Under the condition of pH=1, the content of Na2O in hydrothermal production was as low as 0.0163wt%, which can reduce to 0.0187wt% after calcination at 1200℃.