Abstract: In order to explore the factors influencing the magnetic separation of cobalt and copper in slowly cooled cobalt matte and improve the separation efficiency， the occurrence state of cobalt， copper and iron， composition and dissemination of mineral phases， and their changing characteristics in each sampling points where are located at the top shell， top， middle and bottom shell of the matte bag are studied， by using of optical microscope， scanning electron microscope， electron probe and chemical phase analysis. It was found that①sulfur content in middle part of cobalt matte was significantly higher than that in the shell. The cobalt in the shell was mainly in the form of ferrocobalt alloy with strong magnetism， the cobalt in the middle part was mainly in the form of ferrocobalt sulfide phase with weak magnetic properties， and the cobalt in the upper part (side wall) was in the transition phase of ferrocobalt alloy and sulfide phase. The metal conversion rate of cobalt in the middle of the cobalt matte coating is only 16.35%， which is the main factor affecting the magnetic separation of cobalt and copper. ②ferrous oxide in cobalt matte were oxidized to ferroferric oxide in varying degrees， from the shell to the central， the oxidation degree of ferrous oxide particle in getting more deeply， ferrous oxide particle size distributed in bornite basal phase in microgranular general with less than 0.020 mm， it is hard to be liberated is another major factor in influence cobalt copper magnetic separation. ③in order to improve the metal conversion rate and magnetic separation effect of cobalt in the middle of the slowly cooled cobalt matte bag， it is necessary to regulate the slow cooling temperature in the middle of the high temperature cobalt matte bag， to prevent the segregation of substances with different melting points， especially the low melting point sulfide to the central aggregation； In addition， it is necessary to maintain the reduction environment of matte in the slow cooling process to prevent the ferrous oxide particles dispersed in the base sulfide phase from being locally oxidized into magnetite.

Key words: Slowly cooled cobalt matte, Co-Fe alloy, Co-Fe sulfuration phase composition, Ferrous oxide, Magnetic separation