Novel surface modification approach for graphite anode of lithium ion batteries was developed in this study. Poly(acrylonitrile) was in situ encapsulated on the surface of natural graphite (N-graphite) particles via radiation-initiated polymerization. The graphite obtained shows a large improvement in electrochemical performance such as initial Coulombic efficiency and cycleability compared with the original N-graphite. The structural stability of graphite surface is enhanced due to the fact that encapsulated poly(acrylonitrile) can depress the co-intercalation of solvated lithium ion.