The hybrids of graphene oxide (GO) encapsulated nano-SiO 2 (SiO 2 -GO) were introduced into phenolic resin (PR) to enhance thermal stability of PR. The effect mechanism was investigated in detail. Through electrostatic self-assembly method, the SiO 2 nanoparticles were evenly distributed onto the surface of GO. This structure could not only prevent the aggregation of nano-SiO 2 , but also alleviate the phenomenons of crimp and stack for GO sheets in PR. Nano-SiO 2 and GO showed elaborate synergistic effect on thermal stability of PR. Compared with the pristine PR, the 2 wt% SiO 2 -GO/ PR composite showed higher T 5% , T 10% , and T dmax , which were increased by 65.39, 62.23, and 23.178C, respectively. And the char yield at 8008C increased from 64.78% to 69.38%. Thus, SiO 2 -GO hybrids can facilitate the application of PR in the fields of heat insulation and ablation resistance. POLYM. ENG. SCI., 00:000-000,