The invention discloses a preparation method of a glass fiber mat for precious-metals recovery. According to the preparation method, glass fiber serves as a basal body material, and a felting needle method is adopted to carry out needling on a sedimentary short cut glass fiber cotton bed, so that a fiber web between glass fibers of a carpet veneer is reinforced to prepare a panniform non-woven trapping material; the panniform non-woven trapping material is soaked in a ferric nitrate solution to obtain a fiber composite agent; and the fiber composite agent on the surface layer of a felt body is roughened through erosion in a mixed liquor of nitric acid and phosphoric acid. The glass fiber mat obtained through the preparation method disclosed by the invention has the advantages of high temperature and corrosion resistance, small elongation and contractibility rate and high strength of glass fiber; in addition, fiber of the carpet veneer is of single-fiber and three-dimensional microcellular structure, is high in porosity, has small airflow resistance to nitric oxide, and is a material for capturing precious metal in a high-speed, high-efficiency and high-temperature manner.