The invention pertains to methods of producing aluminum trioxide in the form of powders or agglomerations with particles having a porous honeycomb structure, which can be used as catalyst substrates, adsorbents and filters for the chemical, food, and pharmaceutical industry. The method of production of aluminum oxide in the form of powders or agglomerations with particles having a porous honeycomb structure involves the treatment of the aluminum salt with a solution of an alkaline reagent, washing of the sediment and thermal treatment thereof. The technical result of the invention is the production of aluminum oxide in the form of separate particles with given structure and properties, specifically, with particle porosity of 60-80% and a porous structure represented by extensive parallel channels with near hexagonal packing, with dimension of the channels at the diameter of 0.3 to 1.0 micron and length up to 50 microns. For this, the aluminum salt used is crystals of aluminum chloride hexahydrate, which are treated with an excess aqueous solution of ammonia at temperature of 20-80° C. to form boehmite, and the heat treatment is done at 450-650° C. until aluminum oxide is formed.