In this work, we demonstrate damage-free removal of residual carbon in a dielectric barrier discharge (DBD) plasma for carbothermal-synthesized materials, such as CaAlSiN3:Eu2+ phosphors, SnSb alloy anode materials, and TiN ceramic powders. The efficiency of residual carbon removal and the damaging effects of the plasma for treated materials are investigated in detail, with carbothermal-synthesized CaAlSiN3:Eu2+ phosphors being used as an example. Results show that the residual carbon in carbothermal-synthesized CaAlSiN3:Eu2+ phosphors could be removed effectively within a DBD plasma generator, resulting in the significant improvement of luminescent properties. The damage-free character of this DBD plasma decarburization process to phosphors is revealed, showing amazing superiority over the traditional high-temperature decarburization route. These results offer an attractive strategy for the removal of residual carbon for various carbothermal-synthesized materials with finely controlled compositions.