Abstract: Mechanical properties and particle size composition of a lead-zinc ore in Yunnan were determined, and the problems such as low processing capacity of a section ball mill, substandard fineness and unreasonable particle size composition were solved through the contrast test of grinding medium. The experimental results show that the ore is medium hard and soft ore, with uneven distribution, and high bulk density and toughness. When the grinding fineness is 65% of -0.074 mm, the best effect is obtained. Plan of Φ80mm:Φ60mm:Φ40mm :Φ30mm =20:25:25:30 would improve grinding efficiency and grinding fineness, at the same time reduce the grinding grade levels.