The invention relates to a technology for producing aluminium oxide by decomposing a mineral containing aluminosilicate at a low temperature. The technology for producing the aluminium oxide by decomposing the mineral containing aluminosilicate at a low temperature comprises the following steps of: (1) grinding the mineral containing aluminosilicate, uniformly mixing the mineral containing aluminosilicate with 20-60wt% strong alkali solution at a mass ratio of 1.0: (0.5-2.5), then carrying out a hydrothermal reaction for 1-8 hours in a high-pressure container at the temperature of 200-300 DEG C and the pressure of 2-6MPa, and carrying out solid-liquid separation, thus obtaining potassium mother liquor and aluminium extracting clinker; (2) leaching the aluminium extracting clinker for 20-40 minutes by adopting 5-50wt% acid liquor, wherein the consumption of the acid liquor is 1-10 times weight of the aluminium extracting clinker, filtering, then regulating pH value of a solution containing aluminium to be 8-10, and carrying out solid-liquid separation to obtain filtrate and filter residue; (3) calcining. The technology for producing the aluminium oxide by decomposing the mineral containing aluminosilicate at the low temperature has the advantages of simple technological process, low decomposition temperature, short calcination time, low energy consumption, low production cost, good economic benefit and low pollution to the environment.