Abstract: As a typical difficult-to-machine material, sophisticated and time-consuming polishing methods are often required to smooth polycrystalline diamond. Herein, a non-contact processing method based on atmosphere inductively coupled plasma was used to successfully polish polycrystalline diamond with extremely high efficiency. During the polishing process, oxygen was added into the pure argon plasma to act as reaction gas, generating highly active oxygen radicals which would differentially etch polycrystalline diamond at different position, and finally a smooth surface of polycrystalline diamond could be obtained. Along with the radiation process of oxygen-containing plasma, the tips of grains were removed quickly and the height difference of grains decreased dramatically at the same time. Meanwhile, the Sa roughness of polycrystalline diamond could be reduced from 10.1 μm to 93.7 nm in only 30 min and the material removal rate reached up to 34.4 μm/min, much higher than conventional mechanical/chemical mechanical polishing methods. Further analysis of the composition of polycrystalline diamond indicated that no amorphous carbon or new stress were introduced into the diamond and there was also no change in the crystal plane orientation of grains for polycrystalline diamond. Therefore, this highly efficient plasma polishing method can be well used as a pre-polishing method to rapidly reduce the surface roughness of polycrystalline diamond, and combined with other precision polishing methods, significantly improving the overall polishing efficiency of polycrystalline diamond.