Abstract: A copper−molybdenum ore deposit in eastern Inner Mongolia was processed using a single high-alkalinity lime flotation scheme, which led to low recoveries of copper and molybdenum, high froth viscosity, pipeline scaling, and excessive Ca²⁺ concentrations in the recycled water. To address these problems, a new low-alkalinity combined inhibitor process (lime + BH506) was investigated. Through systematic condition tests and closed-circuit tests, the synergistic pyrite inhibition mechanism of BH506 combined with lime and its effects on copper and molybdenum flotation indices were studied. The results show that under low-alkalinity conditions,lime dosage of 350 g/t, and BH506 dosage of 70 g/t、pH of 8.8, a bulk concentrate with copper grade of 18.62 % and molybdenum grade of 5.02 % is obtained, and the recoveries of copper and molybdenum reach 87.19 % and 84.94 %, respectively, which are 0.12 percentage and 3.10 percentage points higher than those of the original high-alkalinity process. While significantly improving molybdenum recovery, the lime consumption is reduced by 82.50 %, resulting in an annual reagent cost saving of 2.52 million yuan and an annual increase in economic benefit of 86.091 3 million yuan. This study demonstrates that the combination of BH506 and lime enhances pyrite inhibition through a synergistic effect and optimizes the pulp environment, thus providing a reliable technical approach for efficient copper-molybdenum flotation and overall cost reduction under low-alkalinity conditions.