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Graphene is regarded as a prominent multi-functional flame retardant for use in halogen-free flame retardant polymers with simultaneously improved integrated properties and special functionalities.However, its flame retardant efficiency is not impressive enough due to the weak resistance to thermooxidative decomposition. In order to overcome this problem, the surface of graphene oxide was covered with large amounts of non-flammable silicas through a sol-gel and surface treatment process, and then used to modify the epoxy (EP) resin. Results show that the incorporation of the as-prepared nanosilica/ graphene oxide (m-SGO) hybrid into EP resin not only obviously increases the flame retardancy, mechanical, and thermal stability properties, but also endows EP resin with high thermal conductivity, low dielectric loss, and high dielectric constant. Specifically, the peaks of the heat release rate and total heat release of the modified EP resin with 1.5% m-SGO decrease by 39% and 10% of those of neat EP resin, respectively. These attractive features of m-SGO/EP nanocomposites are attributed to the unique structure and high resistance to oxidative degradation of m-SGO as well as its good interactions with EP resin. The investigation provides a new approach for the preparation of novel core-shell flame retardants through surface wrapping with other flame retardants on SGO and related high performance flame retardant resins. † Electronic supplementary information (ESI) available: The chemical structure of SGO and typical data from TG curves of EP and its nanocomposites (PDF). See