Abstract: Graphene oxide (GO) was modified by silane coupling agent 3-triethoxysilyl-1-propanamine(KH-550) and hydrazine hydrate with chemical grafting technology, and functionalized graphene (FG) was prepared. Light-emitting diode (LED) packaged FG/phenyl-silicone rubber composites were synthesized by blending FG and phenyl-silicone rubber through hydrogenated silane method under the effect of platinum catalyst. Effects of modified FG structure, variation of surface functional group and amount on mechanical properties and optical properties of FG/phenyl-silicone rubber composites were studied. Microscopic morphology and thermal stability of FG/phenyl-silicone rubber composites were analyzed. The results show that special functional group are attached on surface of FG modified by KH-550, which will improve the dispersion in phenyl-silicone rubber. Transmittance of FG/phenyl-silicone rubber composites can reach more than 85% by introducing 0.010 0wt% FG in phenyl-silicone rubber, ultraviolet aging resistance properties and mechanical properties were significantly improved. Thermal decomposition temperature of FG/phenyl-silicone rubber composites is 690 ℃, GO/phenyl-silicone rubber composites is 623 ℃, and pure phenyl-silicone rubber is 491 ℃. Heat release of FG/phenyl-silicone rubber composites is lower than that of pure phenyl-silicone rubber. By introducing 0.010 0wt% modified FG in phenyl-silicone rubber, the thermal decomposition temperature of materials will increase by 200 ℃ and heat release decreases which will meet the thermal stability requirements of functional LED composite packaging materials.