Abstract: Taking cassiterite polymetallic sulphide ore as the research object, the effects of preheating and different cooling methods on the grindability of grinding products were investigated after pretreatment of microwave heating. The results showed that after microwave heating, the grindability increased and the Bond work index decreased. This is mainly due to the fact that the microwave radiation increases the temperature of the metal minerals such as jamesonite, pyrite, sphalerite, cassiterite, etc. in the cassite polymetallic sulfide ore, and has less effect on the gangue minerals. The large temperature gradient between the metallic metal minerals and gangue minerals could produce uneven thermal expansion and promote the dissociation of metallic minerals and gangue minerals due to the high stress concentration inside the ore, thereby strengthening the grinding effect.