Abstract: Graphite oxide was modified by KH-550, the modified graphite oxide was reduced to form functionalized graphene (FG) dispersing consistently in the acetone/water (mass ratio is 9∶1) solution by ultrasonic treatment before drying. The FG dispersion was intensively mixed for a certain time by ultrasonic treatment to disperse the nano-FG in α, ω-dihydroxy polydimethylsiloxane matrix and obtained an uniform and stable nano-FG/room temperature vulcanized(RTV) silicone rubber composite after curing. FTIR, TEM, SEM, XRD, and DSC analysis show that KH-550 bonds to the surface of FG sheet to make its layers wrinkled, folding and partially exfoliated, and broaden its layer spacing to 3.46 . FG exfoliates into transparent or semi-transparent layers after ultrasonic treatment. The uniform and wrinkled cross-section morphology of nano-FG/RTV silicone rubber composite, which is different from that of pure silicone rubber, shows that there is no micro-phase separation between the two parts. Compared with the pure silicone rubber, the T_g, T_m and crystallinity of all the nano-FG/RTV silicone rubber composites are improved. Mechanical property tests show that nano-FG reinforces silicone rubber a lot. The tensile strength and the elongation at break of composite with 0.5 wt% nano-FG are 0.43 MPa and 265%, respectively. The tensile strength more than doubles and the elongation at break increases 52% compared with that of pure silicone rubber.