SiC:H surface-modified coatings were fabricated on Reaction Bonded Silicon Carbide(RB SiC) substrates.Silicon was evaporated by E-beam and methane was ionized as reactive gas by End-Hall ion source.X-ray Diffraction(XRD) results show the fabricated film is α phase,its hardness and elastic modulus are in the range of 9.781～13.087 GPa and 89.344～123.413 GPa,respectively.After surface-modification polishing and coating silver,the reflectance of modified RB SiC film is close to that of fine polished Zerodur glass coating with silver.Moreover,the fabricated coatings to the substrate show very good adhesion and no fall-off and cracks in thermal impact test from liquid nitrogen temperature to boiling water temperature for 5 cycles.