Lead−zinc ore is one of the most important nonferrous metal resources in China, and its beneficiation efficiency plays a critical role in improving resource utilization and metallurgical economy. However, conventional single collectors used in flotation usually suffer from poor selectivity, low recovery, and high reagent consumption, making it difficult to achieve both efficient lead recovery and effective gangue suppression. To overcome these limitations, this study systematically investigated the synergistic flotation behavior of butyl xanthate, sodium mercaptobenzothiazole (MBT−Na), and their combined collector systems using a typical lead–zinc sulfide ore. The effects of different collector ratios on the synergistic interaction and flotation performance were comprehensively examined. The experimental results showed that, under conditions of 6.46% Pb grade in the raw ore, grinding fineness of −0.074 mm accounting for 90.21%, zinc sulfate 1 200 g/t, lime 800 g/t, and terpineol 80 g/t, the composite collector achieved the strongest synergistic effect when the total dosage of MBT−Na and butyl xanthate was 140 g/t with a mass ratio of 3:1. Using a closed−circuit process of one rougher, two cleaners, and three scavengers, a lead concentrate with a grade of 71.59% and a recovery of 95.62% was obtained.

Mechanistic analysis revealed that MBT−Na preferentially chemisorbs onto the galena surface, increasing the availability of active sites, while butyl xanthate further enhances surface hydrophobicity and bubble attachment, resulting in a pronounced synergistic flotation effect. This study elucidates the complementary mechanism between MBT−Na and butyl xanthate in galena flotation and provides theoretical and practical guidance for optimizing composite collector systems in the efficient and green beneficiation of complex lead–zinc ores.