Abstract: The investigations of carbon films which are coated on Mo and Hf by using RF sputtering method are presented, including the preparation of carbon films, analysis of the composition of them, their secondary emission and thermal radiation properties and mass analysis of gas released from carbon coated Mo and Hf when heated in vacuum. Main results are: (1) carbon coated Mo can absorb oxygen easily as compared with carbon coated Hf; (2) the maximum secondary emission coefficient of carbon coated Mo or Hf is about 0.7; (3) the carbon coated on Mo is used up at 930℃ or so, but the carbon coated on Hf makes littlechange until 1050℃; (4) considerable amount of CH4 is formed as carbon coated Mo isheated in vacuum.