NOVELTY - A protective film is prepared by adding mixture of polyvinylidene fluoride resin, polymethyl methacrylate resin, titanium dioxide, fluid modifying agent and thermal stabilizer to a first extruder. Mixture of polyethylene terephthalate resin, titanium dioxide, silica, the stabilizer and an antioxidant is added to a second extruder. Mixture of ethylene vinyl acetate resin, UV light absorbing agent, hindered amine light stabilizer, antioxidant, coupling agent and cross-linking agent and promoter is added to a third extruder. Melt in the extruders is allowed to flow to form a composite material.    USE - Protective film for encapsulation of a solar battery.    ADVANTAGE - The film has better anti-weathering property and strong combination force, and is free of solvent pollution, so that probability of generating air bubbles while laminating a solar battery component can be reduced.    DETAILED DESCRIPTION - A protective film is prepared by placing polyvinylidene fluoride resin, polymethyl methacrylate resin, titanium dioxide, fluid modifying agent and thermal stabilizer into a mixer and uniformly mixing the components. The mixture is added to a first extruder under normal temperature and normal pressure, where extrusion temperature of the first extruder is 200-210 degrees C. Polyethylene terephthalate resin, the titanium dioxide, silica, the thermal stabilizer and an antioxidant are put into the mixer and uniformly mixed. The obtained mixture is added into a second extruder under normal temperature and normal pressure, where the extrusion temperature of the second extruder is 250-310 degrees C. Ethylene vinyl acetate resin, UV light absorbing agent, hindered amine light stabilizer, the antioxidant, a coupling agent, a cross-linking agent and a cross-linking promoter are put into the mixer and uniformly mixed. The obtained mixture is added into a third extruder under normal temperature and normal pressure, where the extrusion temperature of the third extruder is 80-100 degrees C. Melt in the first extruder, the second extruder and the third extruder are flowed in a co-current manner by using a multi-runner heat insulated type casting mold head to form a three-layer composite material. The composite material is cooled and formed to obtain a protective film.