Abstract: In order to improve the applicability of microwave-assisted grinding, Hongtoushan copper mine and Sishanling iron mine are taken as the research objects.The ores are pretreated separately with microwave, hydrochloric acid solution, oxalic acid solution and their combination.The heating characteristics, surface morphology and grinding product mass of ores are compared in seven pretreatment methods, and the dielectric constant, wave velocity and microscopic photos are used to reveal the deterioration mechanism of ores.The results show that the dielectric constant of the ores soaked in hydrochloric acid reduces, resulting in the decrease of heating rate and the more even temperature distribution with microwave irradiation.After hydrochloric acid and microwave treatment, there are burning traces on the surface of the copper ore, however, after microwave and hydrochloric acid treatment, there are cracks and obvious mineral boundaries on the surface of copper ore.The surface color of iron ore turns yellow after microwave radiation and is restored after acid treatment.Among the seven pretreatment methods, the combination of microwave and hydrochloric acid gets the best grinding effect.The mass reduction percentage of copper and iron ores are 15.0% and 14.5% respectively.Compared with untreated ores, the mass of grinding product is increased by 58% and 78% respectively.The micro photos and wave velocity results show that the ores generate obvious cracks after microwave irradiation.After ores soaked in hydrochloric acid, the crack width increases furtherly and the deposits appear in crack.The research indicates that combination of microwave and hydrochloric acid can weaken the ore furtherly and improve the grinding effect.