The invention discloses a method for preparing bisphenol F. The method is characterized in that phenol and formaldehyde serving as raw materials and a solid acid catalyst serving as a catalyst are used to prepare the target product bisphenol F, wherein the solid acid catalyst is prepared from heteropoly acid modified clay, and the mass dosing ratio of the catalyst to formaldehyde is (0.01-0.6):1; and the heteropoly acid is one or more of phosphotungstic acid, phosphomolybdic acid, silicotungstic acid, silicomolybdic acid and the like, wherein the clay is one or more of bentonite, kaoline, montmorillonoid, metakaolin, diatomaceous earth and the like. The method has the prominent advantages that the yield of the product bisphenol F is up to 93 percent, the selection to bisphenol F is 96 percent, the catalyst is friendly to environment, the preparation process is simple, the production cycle is short, the catalyst activity and catalytic selection are high, separation and reclamation are easy, recycling is available, and industrialization is facilitated.