The invention relates to a liquid iron pretreatment spray gun positioning device and a positioning method. The liquid iron pretreatment spray gun positioning device comprises a spray gun rack, a lifting car, and further comprises fixed slide blocks, guide slide blocks and supporting frames, wherein the bottom of the lifting car is fixedly provided with a spray gun; the two fixed slide blocks are separately fixed to the two sides of the spray gun rack through the supporting frames; the two sides of the lifting car are fixedly provided with the guide slide blocks; slide slots are formed in the fixed slide blocks; and the guide slide blocks are matched with the slide slots. The liquid iron pretreatment spray gun positioning device has the advantages that: in a desulfurization jetting process, an iron spilling phenomenon caused by shaking the desulfurization spray gun front and back, left and right is almost eliminated; equipment such as the spray gun rack, the lifting car and the like are effectively protected; and the service life of the desulfurization spray gun is remarkably prolonged. The fixed slide blocks are spliced and fixed with the guide slide blocks, so that the occurrence of the phenomenon that the spray gun swings front and back, left and right is eliminated; the splicing areas are increased by virtue of wedge-shaped structures of the fixed slide blocks; and meanwhile, the spray gun is also prevented from moving up and down by matching dead-weight of the lifting car with that of the spray gun.