Previous studies assume that carbon addition at selective sulphidation of laterite nickel ores facilitate the sulphidation of nickel and cobalt in the ores. The presence of carbon in the selective sulphidation of limonitic nickel ores using sulphur was analyzed by thermodynamics and phase transformation. Limonite nickel ores were mixed with 5% sulfur and 4% lignite coal and were formed with pelletizer, roasted at 1000°C for 1 hour (heating rate 10°C/min). Cooled in the furnace by flowed N2 gas. Thermal characteristics of nickel ores pellets show that a number of reactions take place during the heating process at temperatures of 80°C, 280°C, 480°C, 680°C and 960°C. The five reactions are endothermic reactions which are characterized by a decrease in heat flow (μV) on the DSC analysis curve and weight losses on the TGA analysis curve. Addition of 5% sulfur resulted in lower dehydroxylation reaction temperature around 20°C compared to fresh ore. The presence of carbon obtained from the addition of lignite coal resulted in sulphidation reaction did not occurs. Phases formed after roasted are magnetite (Fe3O4) and olivine [(Fe, Mg)2SiO4]. Monosulphide Solid Solution includes troilite (FeS) and marcasite (FeS2) formed in limonite nickel ores mixed with only 5% sulphur without carbon additive when heated at 600°C.