Abstract: Preferential flotation of lead at neutral medium， mixed flotation of zinc-sulfur and separation of zinc-sulfur process were adopted to treat ores in a lead-zinc sulfide ores concentrator of Qinghai province， which caused unstable production and unsatisfactory index. In order to solve the problems， beneficial tests was carried out in the process of preferential flotation of lead at neutral medium， preferential flotation of zinc at alkaline medium and sulfur separation after pulp condition with sulfuric acid. The results indicated that in the case of grinding fineness of -0.074 mm accounting for 55%， lead was selected with one roughing-two cleaning-one scavenging， zinc was selected with one roughing-two cleaning-one scavenging and sulfur was selected with one flotation. The lead concentrate was obtained with lead grade of 70.72%， zinc grade of 2.14%， sulfur grade of 19.98%， gold grade of 1.92 g/t， silver grade of 1 322.45 g/t， lead recovery of 91.78%， gold recovery of 14.28% and silver recovery of 76.29%. The zinc concentrate was obtained with zinc grade of 48.86%， lead grade of 0.26%， sulfur grade of 32.67% and zinc recovery of 97.88%. The sulfur concentrate was obtained with sulfur grade of 47.44%， gold grade of 0.67 g/t， lead grade of 0.11%， zinc grade of 0.17%， sulfur recovery of 64.14% and gold recovery of 80.86%. The new process is more concise， and the production is more stable and smooth. Also， power consumption and reagent costs are reduced. In the same grade index of lead and zinc， the recovery of lead and zinc were increased by 0.50 and 4.32 percentage points， respectively. In addition， the flotation index of associated gold and silver were improved.

Key words: Lead-zinc sulfide ore, preferential flotation, process optimization, neutral medium, alkaline medium