Method for grinding by adding rubber pad between LED sapphire substrate and ceramic supporting is proposed though the ANSYS finite element analysis, which obtains high flatness of the surface of a substrate efficiently. The experimental results also confirmed that after grinding the 2-inch sapphire substrate in the cushion, the total thickness of the error (TTV) <4 microns and the BOW <3 microns. Therefore, the upholstered film is one of the efficient, economic and highly automated ways to grind sapphire substrate.