Abstract: Using sintered highalumina fly ash clinker as raw material， high white aluminum hydroxide was obtained after dissolution， deep desilication and decomposition (carbonation decomposition or seed precipitation) process. Lowtemperature nitrogen adsorption method was adopted to analyze the specific surface area and pore distribution of aluminum hydroxide. The results showed that the aluminum hydroxide adsorption isotherm curve belongs to type III. Aluminum hydroxide pores most belong to micropores， and there still are some mesopores and macropores. The BET specific surface area and average pore diameter of carbonation aluminum hydroxide are much greater than those of seedprecipitation aluminum hydroxide. Driven by the strong action of CO2， aluminum hydroxide precipitates and condenses fiercely in carbonation decomposition， so the crystal structure of aluminum hydroxide is loose and intergranular pores are big. In seed precipitation， the growth of crystal makes the crystal coarsen， the structure is compact and intergranular pores are small.

Key words: aluminum hydroxide, N2 absorption method, isothermal curve, specific surface area, pore characteristics