Chemically vapor deposited diamond films were etched at different parameters using oxygen plasma produced by a DC (direct current) glow discharge and then polished by a modified mechanical polishing device. Scanning electron microscope, atomic force microscope and Raman spectrometer were used to evaluate the surface states of diamond films before and after polishing.It was found that a moderate plasma etching would produce a lot of etch pits and amorphous carbon on the top surface of diamond film. As a result, the quality and the efficiency of mechanical polishing have been enhanced remarkably. 掃描探針顯微鏡(SPM/AFM/STM)