The invention provides a surface plasmon resonance sensing element and a manufacturing method thereof, belonging to the technical field of a sensor for biological system detection. The sensing element comprises a metallic membrane (2), a sensitive membrane and a magnet (3), wherein, the metallic membrane with a chromium membrane and a gold membrane as the sensing elements is plated on the bottom surface of a glass prism (1), the sensitive membrane composed of magnetic nanoparticles (4) subject to surface hydroformylation and an antibody (5) linked with an aldehyde group through a covalent bond is made on the metallic membrane, and the magnet is arranged under the glass prism. The manufacturing method of the sensing element comprises the following steps: preparation of the metallic membrane, preparation of Fe3O4 magnetic nanoparticles, preparation of ammoniated SiO2-coated magnetic nanoparticles, preparation of magnetic nanoparticles subject to surface hydroformylation and preparation of the sensitive membrane. The invention has the advantages of simple manufacturing process, high sensitivity, good biocompatibility and good selectivity and can be used in all antibody and antigen detection and protein and drug measurement.