The invention relates to an infinitely hot-bendable polyester protective film as well as a preparation method and application thereof. The protective film comprises a surface protective film layer, a high-wear-resistance anti-fingerprint hardened layer, an infinite polyester base film, a high-viscosity pressure-sensitive adhesive layer and a release film layer which are sequentially attached. The polyester protective film disclosed by the invention is high in light transmittance and low in haze, does not affect an under-screen fingerprint unlocking function, has excellent AF water drop angle screen fitting property, is good in hot bending and shaping effect, and does not warp when being attached to the edge of a curved screen; the surface of the base film has high pencil hardness, wear resistance, scratch resistance, fingerprint resistance and high smoothness; the film is relatively good in wettability and exhaust property when being attached to the screen, and is not easy to leave fingernail imprint. The protective film has the advantages of simple structure, low requirements on polyester base film coating equipment, easiness in realization of process parameters, wide applicability, few production procedures and low cost.