The invention relates to a method for preparing magnesia, silicon dioxide and nickel oxide products from lateritic nickel ores. The method comprises the following steps: (1), crushing, grinding and roasting the lateritic nickel ores with ammonium sulfate; (2), dissolving and filtering roasted products; (3), evaporating, condensing and crystallizing filtrate to prepare magnesium sulfate; (4), dehydrating and calcining the magnesium sulfate to prepare magnesia; (5), reacting filter residue with an alkaline solution or molten caustic soda, leaching and filtering the product of reaction to obtain a sodium silicate solution; (6), carbonizing, decomposing, filtering, washing and drying the sodium silicate solution to prepare the silicon dioxide; (7), leaching and filtering the residual filter residue by an ammonium carbonate solution; and (8), distilling ammonia from the filtrate and calcining the filtrate to prepare the nickel oxide. The residual residue is ferric oxide containing a small amount of impurities and can be used as an iron-making raw material or deep processed into a product with a high added value. The method is suitable for processing various lateritic nickel ores, has simple technological process and simple and convenient equipment, does not emit solid, liquid and gas waste or cause secondary pollution and uses lower cost to realize the high added value comprehensive utilization of lateritic nickel ore resources.