The invention proposes an oil-immersed surface plasmon resonance (SPR) superlens with a high numerical aperture. One side of the superlens is a special optical aspheric surface whose surface topography is designed by the invention, and the other side is an optical plane. The coupling lens is in axial symmetry in a normal direction of the center of the optical plane, and the cross section parallel to the optical plane of the lens is circular. The coupling lens is made of material with a high index of refraction which is transparent to visible light, parallel light enters the lens in parallelism with an optical axis from one side of the optical aspheric surface, and through refraction by the special optical aspheric surface and a matching oil layer, the parallel light is focused on the focal point of the superlens. When the numerical aperture of the coupling superlens is larger than 1.05, the superlens can be used for exciting surface plasma. The oil-immersed surface plasmon resonance (SPR) superlens with a high numerical aperture can serve as an effective substitute of an oil-immersed microobjective with a high numerical aperture, and has the advantages of simple structure, low cost, definable working distance and the like.