Preparation method of magnetic nanoparticles with core-shell structure was introduced, especially focusing on the preparation principle of sol-gel method, microemulsion method, and self-assembly technique. The application of core-shell nanoparticles in precision machining was discussed. The Fe₃O₄@SiO₂ composite particles were prepared by sol-gel method and were applied to the magnetorheological polishing of titanium alloy plates. Results show that core-shell nanoparticles with higher surface quality can be obtained after processing, compared with those after conventional abrasives. After polishing for 20 min, the surface roughness of the workpiece reaches 23 nm and the scratches are effectively reduced. Finally, the preparation and application of core-shell nanoparticles are summarized and prospected to provide a reference for further research on core-shell nanoparticles.