The invention discloses a diamond single crystal surface metallization treatment method. The method comprises steps as follows: the surface of a diamond single crystal is bombarded and sputtered with Fe, Co or Ni as a source electrode target material with a double-glow plasma diffusion metallizing technique; the single crystal is soaked in an acid solution, so that remaining metal and graphite are removed; a metal diffusion coating is prepared on the surface of the diamond single crystal with strong carbide metal as a target material with a double-glow plasma diffusion metallizing technique. Uniformly distributed micro pits are formed in the surface of the single crystal under the bombardment and sputtering functions of the double-glow plasma and the graphitized catalytic function of Fe, Co, Ni and other iron group metals, surface roughening and activation are realized, strong carbide metallic elements react with a part of carbon atoms on the surface of the diamond so that chemical bond combination is realized, and the bonding strength of the surface metallization coating and the single-crystal diamond is improved. Bombardment etching and metallization treatment are realized with one device, the process is simple, the cost is low, and the method is suitable for industrial production.