The invention belongs to the technical field of mineral processing engineering and relates to a step-by-step desiliconizing and upgrading method for high-aluminum and high-silicon bauxite. The method comprises the steps that firstly, the high-aluminum and high-silicon bauxite is subjected to rough grinding, slurry mixing is conducted, a spiral chute is adopted to conduct the first step of desiliconizing, and coarse grain bauxite concentrate ores are obtained through roughing and concentrating; secondly, middlings in the first step are combined and reground, slurry mixing is conducted, the second step of desiliconizing is conducted through a hydraulic cyclone and the spiral chute in sequence, specifically, desliming is conducted through the hydraulic cyclone firstly, settled sand of slime is subjected to roughing and concentrating through the spiral chute, and medium grain bauxite concentrate ores are obtained; and thirdly, the middlings and tailings obtained in the first and second steps are combined and subjected to floatation desiliconizing, fine grain bauxite concentrate ores are obtained through a closed floatation process. By means of the step-by-step desiliconizing and upgrading method that the coarse grain ores are enriched in the spiral chute after rough grinding, after the middlings are reground, the medium grain ores are enriched in the hydraulic cyclone united with the spiral chute, and tailing fine slime flotation is conducted to enrich the fine grain ores, the bauxite concentrate ores of different grain grades are obtained by stages, so that the step-by-step desiliconizing and upgrading method has the advantages that drug consumption is low, the recovery rate is high, and desiliconizing is thorough.