Abstract: The first domestic thermo-chemical polishing apparatus is setup. Three φl10 mm in diameter diamond films can be polished simultaneously at 10^-3Pa from 750℃ to 100℃, with the polishing rate increasing with increasing temperature. The results of polishing at 980℃ showed that polishing of CVD diamond films is very efficient. Thermo-chemical polishing mechanism is based on the transformation of diamond into graphite and the atomic dissolution of carbon into a hot metal.