An advanced tin oxide-coated tin in graphite (Sn@SnO x /C) nanocomposite is synthesized with a one-step method of dielectric barrier discharge oxygen plasma-assisted milling (O2-P-milling). Synergetic effects of rapid plasma heating and impact stress act on the tin/graphite powder during O2-P-milling, and SnO x (1≤ x ≤2) is generated in situ on the Sn surface from the reaction between Sn and oxygen. The resulting composite possesses a unique microstructure, where Sn nanoparticles coated by an ultrathin amorphous/nanocrystalline SnO x layer are homogeneously embedded within a graphite matrix. As lithium ion anodes, the Sn@SnO x /C nanocomposites display superior electrochemical performance to Sn–C and Sn–SnO2–C nanocomposites milled under argon plasma. The SnO x /C nanocomposite obtained after O2-P-milling for 25h that contains a high content of amorphous/nanocrystalline SnO x exhibits a high capacity retention of 500mAhg−1 at 250mAg−1 after 70 cycles, indicating that O2-P-milling is a promising method to prepare Sn-based multiphase nanocomposite anode materials.