In order to investigate the influence of different magnetic field strengths on the mechanical property and wear resistance of nickel-based alloy, GH99 nickel-based alloy specimen was subjected to pulsed magnetic treatment by the pulsed strong magnetic field equipment. Through the microstructure observation, the wear mechanism and strengthening mechanism of GH99 nickel-based alloy were analyzed. Results show that the applied pulsed magnetic field improves the material dislocation distribution and reduces the dispersion of residual stress on the specimen surface. At the magnetic field strength of 10 T, the residual compressive stress reaches the maximum value (-223.45 MPa). The tensile fracture of the material is mainly characterized by the ductile fracture. This is because the pulsed magnetic field treatment of the alloy produces sub-structured dislocation cells, which contributes to the fine grain strengthening effect. In addition, the surface microhardness and wear resistance of the specimen are firstly increased and then decreased with increasing the magnetic field strength from 0 T to 15 T. The dislocations inside the alloy proliferate under the pulsed magnetic field, increasing the dislocation density and resulting in the phenomenon similar to the process hardening. However, excessive magnetic field strength may lead to the dislocation plugging, resulting in severe distortion of the cell dot and deterioration of material properties.