This application provides a silicon-based material, a preparation method thereof, and a secondary battery, a battery module, a battery pack, and an apparatus associated therewith. The silicon-based material includes a core structure and a coating layer provided on at least partial surface of the core structure, where the core structure includes both a silicon phase and a lithium metasilicate phase, and a particle size P of the lithium metasilicate phase is ≥30 nm. The silicon-based material of this application can not only increase energy density of a secondary battery with the silicon phase, but also improve structural stability and chemical stability of the silicon-based material, so that the secondary battery can deliver satisfactory and balanced cycling performance and first-cycle coulombic efficiency in overall.