The invention relates to the field of producing aluminum oxide with bauxite, and especially relates to a method for producing aluminum oxide with low-grade high-sulfur bauxite. The method comprises the following steps: (1) a mineralizing agent is added into low-grade high-sulfur bauxite; under roasting, SiO2 in bauxite is converted into active silicon; flue gas is desulfurized and discharged; (2) the roasted bauxite is treated with a sodium hydroxide solution; the A/S of desiliconized bauxite can be improved to 6-14; (3) the desiliconized bauxite is subjected to solid-liquid separation, such that a sodium silicate solution and high-grade bauxite are obtained; (4) the high-grade bauxite obtained through the solid-liquid separation process is used for producing metallurgical-grade aluminum oxide with a Bayer process; (5) the sodium silicate solution obtained through the solid-liquid separation process is directly evaporated to produce a sodium metasilicate product or is added into lime milk for producing an active calcium silicate product and a sodium hydroxide solution; the sodium hydroxide solution is returned to the desiliconization process. With the process flow provided by the invention, low-grade high-sulfur bauxite roasting desulfurization, silicon mineral activation and chemical desiliconization are realized. The method has low cost and high economic benefit.