Abstract: In a low-grade lead-zinc ore in southwest China， the lead grade is 2.99% and the zinc grade is 1.57%. The associated silver grade in the ores is 10.80 g/t. Both lead and zinc mainly exist in the form of sulfide. In order to efficiently develop and utilize the low-grade ores， the heavy liquid floating sinking test and the flotation conditions tests of the raw ore were studied. The results showed that: ① The tests for floating sinking were carried out with heavy liquid aiming at the raw ores below 12 mm. When the density of heavy-medium suspension is 2.7 kg/m3， the lead grade and zinc grade of density greater 2.7 kg/m3 product are 10.48% and 5.37%， respectively， which is nearly three times higher than that of the raw ores. The loss rates of lead and zinc in density less than 2.7 kg/m3 products were 4.48% and 6.62%， respectively. ② The lead concentrate with lead grade of 69.26% and lead recovery rate of 95.21%， and zinc concentrate with zinc grade of 59.83% and zinc recovery of 84.26% were finally obtained from the raw ore in the low alkalinity pulp system by the flowsheet scheme of lead priority floatation， zinc and sulfur mixing flotation and then separation. The research results showed the feasibility of pre-separation and low alkalinity flotation of the ore， which has certain practical significance for the development and utilization of this kond of low grade lead-zinc ore.

Key words: low-grade, lead-zinc sulfide ore, pre-selection with heavy medium, flotation