The invention discloses a magnetic nylon composite material. The magnetic nylon composite material is prepared from the following components in parts by mass: 70-85 parts of magnetic powder, 8-15 parts of nylon 6 resin, 15-30 parts of asphalt, 1-3 parts of a compatibilizer and 1-3 parts of a processing aid. The invention further discloses a preparation method for the composite material. The preparation method comprises the following steps: 1) treating magnetic powder; 2) mixing the magnetic powder with nylon 6 resin, the compatibilizer and the processing aid; 3) soaking mixed base stock obtained by mixing into a carbon tetrachloride solution of asphalt; and 4) treating by a twin-screw extruder to obtain the magnetic nylon composite material. The magnetic nylon composite material is excellent in performance, has tensile strength of 65 MPa or more, has bending strength of 120 MPa or more, has cantilever beam notch impact strength of 5.5 KJ/m<2> or more, and has a wide application prospect.