Abstract: Taking aluminous slag of clay nickel ore acid soaking liquid as raw material, high purity Al(OH)3 powder was successfully prepared through alkali extraction and split-step carbonation. The influences of the alkali extraction temperature and pH value on the Al dissolution rate of aluminous slag, and the pH value of carbonation end and carbonation temperature on the Al precipitation rate were also investigated, respectively. The appropriate alkali extraction conditions were pH value of 14, temperature of 90°C and time of 10 min, and the carbonation conditions were the pH value of the carbonation end of 9 and temperature of 75°C, respectively. The Al(OH)3 powder was characterized using XRD, SEM and chemical component analysis. The results indicate that the crystal of Al(OH)3 powder grows well, and the particles of Al(OH)3 are irregular with rough surface, loose and porous structure.