Presented are the results of the studies on the calcium ferrite-base slags which have recently received attention, because their properties give promise in reducing the troubles caused by iron silicate-base slags, such as magnetite precipitation, high viscosity and loss of valuable metals. Calcium ferrite slag was equilibrated with metallic copper under a controlled partial pressure of oxygen by using a mixture of CO//2 and CO. The experiments were carried out with lime or magnesia crucibles at the temperature range of 1150 degree C to 1350 degree C. It was found that the solubility of copper in the slags is affected by oxygen potential and temperature and corresponds to the amount of 70% in comparison with the iron silicate slags case. Empirical equations for the ratio F** plus ** plus ** plus /F** plus ** plus and for iron contents in metallic copper are shown.