To promote the thermostability of methylsilicone resin, toluene-2,4-diisocyanate (TDI) modified graphene oxide (GO) was grafted on silicone resin. Fourier-transformed infrared (FT-IR) spectra suggested that modified GO was grafted on silicone resin successfully. Thermogravimetric analysis (TGA) curves showed the initial decomposition temperature of modified methylsilicone resin increased from 391.2 oC to 427.0 oC, maximum weight loss rate temperature increased from 423.5 oC to 542.5 oC, indicated that the incorporation of modified GO could obviously improve the thermostability of methylsilicone resin. The effects of GO on the methylsilicone resin were also characterized to assess the degradation behavior of methylsilicone resin. Furthermore, the mechanism of improving the thermostability of methylsilicone resin by modified GO was also discussed: Reducing remaining Si-OH in the curing process of silicone resin; isolating oxygen atoms and other substances, hindering the thermal movement of the silicone resin chain can effectively improve the thermostability of the silicone resin.