Abstract: Several factors which causing the mass changes of the steel melts in the crucibles have been analysized in detail, during such experiments on decopperization by adding ammonium compounds into the steel melts to imitate the wire-feeding in steelmaking. On basis of this, an expressin of the relation between the copper content of the melt and the amount of added decopperizing agent was developped, by virtue of which the data were reprocessed. The obtaied results are more reasonable than those not reprocessed.