The new type of silicone rubber prepared by organosilicon polymer containing special groups presents the tensile strength of 3.92 MPa and the elongation at break of 285%. Compared with Sylgard(r)184 silicone rubber (Dow Corning Corporation), it has better high temperature resistance and almost no weightlessness from room temperature to 430℃. Thermogravimetric analysis was conducted to research the thermal degradation at different temperatures and the heat pyrolysis products were trace determined by FT-IR. The results show that with the increase of temperature, the organic groups of products are gradually decomposed. Organosilicon rubber is gradually changed into the typical inorganic SiCO compounds in the process of pyrolysis. Elemental analysis and X-ray photoelectron spectroscopy results show that the pyrolyzates are mainly composed of Si, C and O elements above 1050℃. X-ray diffraction analysis showes that partial β-SiC crystal structure is brought about gradually from the pyrolysis products at 1050℃ to 1500℃ under nitrogen atmosphere. With the treatment temperature rising, the crystallinity of SiC and cristobalite obviously increases.