In order to effectively reduce the sintering carbon emission from the limonite - type laterite nickel ore, promote the formation of liquid phase in its sinter, and strengthen the structural strength of its sinter, the sintering reaction mechanism of this limonite - type nickel ore under different temperature and alkalinity conditions in a carbon - free sintering environment is investigated by using a carbon - free sintering method and based on thermodynamic analysis. The results show that: the temperature of carbon - free sintering has a significant effect on its liquid phase production; the increase of alkalinity can promote the further melting of Fe₂O₃ into the liquid phase, and the calcium ferrite minerals gradually rise and the spinel minerals gradually decrease; at the alkalinity higher than 1.6, more voids and cracks appear in the carbon - free sinter with the increase of alkalinity; under the same alkalinity condition, the carbon - free sintering could generate with enough main liquid components spinel - like minerals and more compact sinter microstructure.