Abstract: There is 0.24% copper and 85.00 g/t silver in a copper silver polymetallic ore from Wuping.On the basis of flotation conditioning experiments on conventional crushing-grinding process (CCG) products and final high pressure grinding roller(HPGR) grinding system products respectively，closed-circuit flotation tests were conducted at optimum copper and silver bulk flotation-separation of copper from silver conditions，respectively.Results indicated that，beneficiation index on final HPGR grinding system is better than that of CCG.Particle size distribution curve and metal volume distribution curve for both CCG process and final HPGR grinding system were analyzed by least square method.Results indicated that final HPGR grinding system products were higher than that of CCG process in the yield of suitable flotation fraction and easily to be recycled metal quantity；variance on particle size distribution and metal quantity distribution of final HPGR grinding system is much smaller than that of CCG process.Liberation degree of valuable minerals analyzed by MLA(Mineral Liberation Analyzer) show that:liberation degree of suitable flotation fraction(0.01~0.1 mm) by final HPGR grinding system is much higher than that of CCG process.Thus，separation indexes of final HPGR grinding system is much better than the CCG process.The experiments results provide a new clue or method for reduce energy consumption of grinding in mineral processing fields.

Key words: Copper-silver ore, Final grinding by high pressure grinding rolls, Mechanism analysis, Least square method, MLA