The invention provides a baking-free brick prepared by using yellow phosphorus slag and modified phosphogypsum as raw materials and a preparation method thereof. The industrial waste yellow phosphorus slag and the modified phosphogypsum are used as basic raw materials, sand and cement are added into the raw materials, and the mixture in a weight ratio is prepared into a finished product by processes of crushing, proportioning, mixing, stirring, high-pressure shaping, stripping, steam curing and the like. A large amount of yellow phosphorus slag discharged by the yellow phosphorus industry and a large amount of phosphogypsum discharged by the phosphoric acid industry are comprehensively utilized, and meanwhile, various environmental pollutions caused by long-term stacking of the yellow phosphorus slag and the phosphogypsum are reduced. The baking-free brick prepared from the yellow phosphorus slag and the phosphogypsum has the advantages of high utilization rate of industrial waste slag, high consumption, simple production process, short production period, low cost, environmental protection and energy conservation; and the brick meets the national standard requirements for baking-free common bricks, and is a novel environment-friendly building material. The steam curing is performed on the formed brick blank so as to shorten the curing time, improve the compressive flexural performance of the brick and facilitate large-batch production.