Radiation is one of the key processes of energy transport in high-temperature arc plasmas. In high-pressure SF6 arc, the copper vapor resulting from electrode erosion shows significant influences on the radiation transport in SF6 arc. In order to provide the basic data of radiation for the simulation of SF6 arc with consideration of electrode erosion, the calculation model for net emission coefficients (NEC) of SF6-Cu arc in high-voltage circuit breakers was established in this work based on the study of atomic lines, atomic continuum, and molecular spectrum. The effects of arc radius, arc pressure, and copper concentration were analyzed on the NEC of SF6-Cu arc. It is found that the resonance lines and non-resonance lines dominate the NEC at low and high temperatures respectively. With the increase of arc radius, the values of NEC are reduced. With the increase of arc pressure, the values of NEC are raised. The existence of copper vapor strongly raises the values of NEC because copper is easier to ionize and excite than nonmetallic elements such as fluorine and sulfur.