Core-shell nanocomposites have received more and more attention from scholars in recent years due to their excellent properties. This paper introduces the preparation method of magnetic nanoparticles with core-shell structure, focusing on the principle of sol-gel method, microemulsion method, and self-assembly technology. The recent research progress on the application of core-shell nanoparticles in precision machining is reviewed. Then, the Fe3O4@SiO2 composite particles were prepared and applied to the magnetorheological polishing of titanium alloy plates. The results showed that higher surface quality can be obtained after processing core-shell nanoparticles compared to conventional abrasives. After 20 minutes of polishing, the surface roughness of the workpiece reached 23 nm and the scratches were 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.