Abstract:The paper introduced a method of increasing grinding quality and efficiency, reducing ball consumption by changing ball diameter and proportion within ball mill. The ball diameter and proportion of addition was calculated by ball diameter semi-theory formula on the basis of the ore-bearing rock mechanics properties and the grinding conditions of Dongguashan copper mine,it is m(Ф60):m(Ф40)=45:55. The results of industrial experiment indicate that, the grinding fineness (-0.074mm) and middle dressing size fraction(0.15 0.01mm) contents increased 7.60 and 5.76 points respectively, the unqualified coarse fraction ( 0.15mm) contents and over grinding (-0.01mm) reduced 2.9 and 2.86 points respectively, The mill utilization efficiency raised 9.8%, ball consumption reduced 10.52% after used new ball diameter and proportion of addition. Ball diameter semi-theory formula has computation is easy and the grinding effect is significant, so it has broad application prospects and value for popularization.