By carbothermal reduction of MgO with black carbon as reduction agent at a high temperature, MgO was deposited on the surface of MgO-CaO clinker (as coating) to improve the clinker’s hydration resistance. In the paper, effect of deposition temperature and holding time on the hydration resistance of the treated MgO-CaO, the deposition mechanism and MgO coating kinetics were investigated with hydration resistance test, Xª²ray diffractometry (XRD) and scanning electronic microscope (SEM). Results showed MgO coating grew in a 2D mode on the surface of MgO-CaO particles; the MgO coating improved  the hydration resistance of the coated MgO-CaO clinker, and the coated clinker would become stronger when coated at higher deposition temperature and longer holding time. The measurements also found that MgO deposition process varied with the deposition temperature: it was mainly a chemical-controlled process at temperatures between 1 400-1 500 ¡æ, with an apparent activation energy (AAE) of 97.8 kJ·mol-1;it would change into a diffusion-controlled process when the temperature rising to 1 500-1 600 ¡æ, with apparent activation energy of 19.2 kJ·mol^-1.