The invention discloses a surface modification ricinus communis fiber and a preparation method and application thereof. Surface modification ricinus communis is ricinus communis fiber with an epoxy-terminated hyperbranched polymer grafted onto the surface of the ricinus communis fiber, and the epoxy-terminated hyperbranched polymer is obtained by blocking a hydroxy-terminated hyperbranched polymer through an epoxy group blocking agent. The preparation method of the surface modification ricinus communis fiber comprises the following steps that 1, the ricinus communis fiber is subjected to silanization treatment; 2, the hydroxy-terminated hyperbranched polymer is grafted onto the ricinus communis fiber surface through condensation polymerization, the epoxy group blocking agent is adopted for blocking, and the surface modification ricinus communis fiber is obtained. The surface modification ricinus communis fiber is applied to serve as a bisphenol A type epoxy resin toughening and reinforcing agent. Accordingly, the interface bonding capacity and adhesion force of the surface modification ricinus communis fiber and an epoxy resin substrate are excellent, the surface modification ricinus communis fiber is used as the toughening and reinforcing agent of the bisphenol A type epoxy resin, the resin toughness can be improved, and meanwhile the tensile strength, the tensile modulus, the bending strength and the bending modulus can be greatly improved.