Abstract: This is a paper in the field of mineral processing engineering. Copper smelting slag is a kind of important secondary resource of copper. Crushing is the basis and prerequisite for the separation and enrichment of copper minerals in copper smelting slag. Based on the analysis of process mineralogy, the mechanical properties of the main copper minerals, natural copper and chalcocite, and the main gangue mineral glass in copper smelting slag were determined, including uniaxial compressive strength, bending strength, impact strength, and ductility. The relationship between mechanical properties of minerals and grinding were studied. The results showed that the main copper minerals, natural copper and chalcocite, in copper smelting slag were with lower uniaxial compressive strength, bending strength, and impact strength than glass, so they were both more likely to be crushed than glass.Natural copper had better ductility to be ground in the form of coarse-grained flakes and could be separated from other minerals. Poor ductility of chalcocite made it easier to be ground into fine-grained products.The grinding results of copper smelting slag were consistent with the analysis of mineral mechanical properties, which indicated that it was effective and feasible to analyze and study the mineral crushing by mineral mechanical properties.