The invention belongs to the technical field of a dental biological medical material and particularly relates to a tooth desensitizer containing phosphosilicate glass as well as a preparation method and application thereof. After the phosphosilicate glass is contacted with a phosphate buffer solution, artificial saliva or simulated body fluid, phosophate ions as well as calcium, strontium, magnesium, zinc, potassium or sodium ions can be released rapidly, a SiO2-enriched silica gel layer is formed on the surface of a material, Ca<2+> and PO4<3-> form a CaO-P2O5 amorphous layer on the SiO2 silica gel layer and the CaO-P2O5 amorphous layer is crystallized to be transformed into hydroxyapatite (HA), so that a dentinal tubule is rapidly closed and hemodia is treated. After the phosphosilicateglass and composite resin are compounded, the phosphosilicate glass is rapidly photocured through photo-initiated polymerization curing to cover the surface of a tooth, so that the dentinal tubule canbe closed rapidly and the hemodia is treated. The tooth desensitizer can block the dentinal tubule rapidly and effectively and induce a dentin layer to be rapidly repaired.