The invention discloses an ultraviolet light-cured biomass epoxy acrylate prepolymer and a synthesizing method and application thereof. The synthesizing method comprises the following steps of using cardanol as a main raw material, enabling phenolic hydroxyl in cardonol molecules and epichlorohydrin to react, enabling double bonds in the cardonol molecules and hydrogen peroxide to react so as to lead in a plurality of epoxy groups, and then reacting with (methyl)acrylic acid, so as to synthesize the ultraviolet light-cured biomass epoxy acrylate prepolymer. The synthesizing method has the advantages that the method is novel, the operation is simple, and the repeatability is good; the synthesized biomass epoxy acrylate prepolymer contains a cardanol group, so that a product has better hydrophobic property and chemical reagent-resistant property, the viscosity and rigidity of the product are correspondingly improved, and the prepolymer can be applied to the fields of ultraviolet light-cured coatings, ink, adhesives and the like.