The invention relates to a method for producing 
aluminium oxide and a by-product 
silicon by low-temperature alkali 
digestion of low-grade 
bauxite, and belongs to the technical field of 
aluminium oxide production. The method comprises the following steps: firstly, smashed low-grade diasporic 
bauxite and a circulating mother liquid are grinded to form a mineral 
slurry; secondly, a 
digestion reaction is performed enable 
kaolinite in the mineral to be dissolved, react and enter a solution, 
filtration residues are high-grade 
bauxite concentrate, and the high-grade bauxite concentrate is processed for produce 
aluminium oxide and low-alkali 
red mud by adopting a 
Bayer process; 
sodium aluminosilicate in a filtrate is subjected to desilication reaction, so that 
sodium-
silicon residues, and a filtrate containing 
aluminium oxide, 
silicon oxide and 
sodium oxide are obtained; and finally, the filtrate is supplemented by 
sodium hydroxide, and the supplemented filtrate is used as the circulating mother liquid to return for preparation of the mineral 
slurry through 
grinding, and part of the sodium-silicon residues are used as a 
seed crystal to return to a desilication process, and the other part of the sodium-silicon residues are used to prepare silicon products such as molecular sieves. The method is a whole-procedure wet treatment process, aluminium and 
silicone are fully extracted from the bauxite for preparing the corresponding products, also alkali consumption in the 
red mud during the 
Bayer process is substantially reduced, the alkali content in the 
red mud is reduced, and recycle value of the red mud is improved.