The present invention settles the problem of a plurality of foams in the lead-zinc sulfide ore flotation, serious lead metal settlement phenomena and large loss of lead metal, and provides a dosing system for the lead flotation technique, which can promotes the lead recovery rate effectively. The key point is that butyl xanthate is added during the lead separation. The concentration of a butyl xanthate water solution is 2.5-15 percent. The amount of butyl xanthate added with the concentration of 5 percent is 5g/t-15g/t. The concentration of an ore slurry is 30-40 percent, and the pH value of the ore slurry is 9.5-11.5.