The invention relates to the technical field of protective films, in particular to an UV viscosity reducing composition, an UV viscosity reducing film and a preparation method thereof. The UV viscosity reducing composition is prepared from the following main raw materials in percent by weight: 20-50% of high temperature-resistant acrylate pressure-sensitive adhesive resin, 1-30% of a polyfunctional oligomer and/or polyfunctional monomer, 0.3-2% of a crosslinking agent, 0.1-5% of an antistatic agent, 0-2% of a dispersant, 0.2-2% of a leveling agent, 0.5-5% of a photoinitiator and 25-60% of a solvent. The UV viscosity reducing film comprises a substrate layer, an UV viscosity reducing layer coated thereon and a release film layer. The UV viscosity reducing composition has an excellent adhesive force, has a high adhesive force and a high release force before UV irradiation, has a low adhesive force, a low release force and a good antistatic effect after UV irradiation, and can resist 120DEG C high temperature for 30 minutes without an adhesive residue.