The invention aims at the problem that an automobile exhaust purification spent catalyst is smelted into iron alloy containing platinum group metal through a pyrogenic method, in the acid dissolutiondeironing pretreatment process, the acidity, the temperature, the liquid-solid ratio, the feeding speed and other key parameters are difficult to determine, thus, part of platinum group metal is dispersed in a solution in the dissolution process, and precious metal is dispersed and lost. According to the acidolysis pretreatment method for the iron alloy containing the platinum group metal, dispersion of the platinum group metal in the solution is controlled by controlling the reaction temperature, the acidity of hydrochloric acid, and other technical parameters through the segmented adding mode, the content of the platinum group metal in the solution is smaller than 0.0005g/L, the problem that the platinum group metal is lost is solved, the secondary recovery procedure is simplified, and the production cost is reduced.