The metals reduction processes by carbon and its monoxide in the FeS-Ni S-CaO system under continuous heating conditions up to 1250 °C nave been studied by means of thermogravimetric analysis together with differential thermal that as well as mass spectrometry of the gases. During heating in an inert atmosphere in FeS-CaO and FeS-Ni3S2-CaO systems along with the sulfide phases the formation of CaFeSO and Ca3Fe4S3O oxysulfides has been revealed. The carbo- thermical reduction chemistry of FeS, Ni3SO and F45Ni45S8 sulfides together with calcium oxide has been established. It has been shown the reduction products are calcium sulfide and metals, the calcium oxide insertion preventing sulfurous gassing. For temperature range 750-1170 °C the experimental data on metals carbothermal reduction in FeS-Ni3S2-CaO system are denoted by one-step Avrami-Erofeev model with a limited stage of the formation and growth of nucleuses the and kinetics parameters equaled E = 520 kJ/mole, logA = 1 8.2 s-1, n = 0.87. It has been shown the reduction of nickel sulfides by a carbon and its oxide is activated by means of the insertion to the reaction mixture composition of iron sulfide along with calcium oxide that contributes the formation of intermediate iron-calcium oxysulfide compounds having a higher reactivity.