The present invention discloses a method for producing building gesso by using semi-hydrated phosphogypsum and dihydrate phosphogypsum, and belongs to the field of building gypsum production, wherein the building gesso has characteristics of small water requirement of normal consistency and high strength. The method comprises processes of raw material calcination, grinding and aging, wherein the raw materials comprise, by weight, 5-60% of semi-hydrated phosphogypsum, and 40-95% of dihydrate phosphogypsum. According to the present invention, the match use of the semi-hydrated phosphogypsum andthe dihydrate phosphogypsum is adopted, and the ratio of the semi-hydrated phosphogypsum to the dihydrate phosphogypsum is strictly controlled, such that the disadvantage of single use of the semi-hydrated phosphogypsum or the dihydrate phosphogypsum is overcome, performances of the semi-hydrated phosphogypsum and the dihydrate phosphogypsum can be supported each other, and the prepared building gesso has characteristics of small water requirement of normal consistency and high strength; and the phosphogypsum is adopted to replace the natural gypsum to produce the building gesso so as to reduce production cost, change the phosphogypsum waste into treasure, effectively treat pollution and hazard on the environment due to phosphogypsum waste, and provide good environmental benefits, social benefits and economic benefits.