Silicone rubber foam combines the excellent characteristics of silicone rubber and foam material, could be widely used in aerospace, vehicle engineering, electronics and medical field of shock damping, sound insulation, electrical insulation and physiological inert materials. Traditional foaming methods (such as chemical foaming method and leaching method, etc.) have residual problems of foaming agent or pore-forming agent, which would affect the product performance and even harm human health. Silicone rubber foams with different cell morphologies (spherical cells and polygonal cells), porosities (from 51.4% to 82.6%) and average cell sizes (from 5 μm to 266 μm) have been designed by green supercritical CO2 foaming in this research. The relationship between rheological behavior, cellular structure and mechanical properties have been investigated, and the cellular failure mechanism under stress has been also analyzed. This research could provide an eco-friendly and a convenient way to design the cellular structure of silicone rubber foam based on its practical application.