Three 2-mercaptobenzimidazole derivatives,1-ethyl-2-mercapto-benzimidazole(EMBI),1-propyl-2-mercapto-benzimidazole(PMBI)and 1-benze-2-mercapto-benzimidazole(BMBI),were designed and synthesized in the paper,and their collecting behavior in flotation separation process of galena over pyrite was investigated by flotation tests on lab scale.Apart from this,density functional theory(DFT)calculation and molecular dynamics(MD)simulation were also used to elucidate their collecting mechanism.Results of flotation tests indicate that separation of galena over pyrite is feasible at pH 10,and BMBI has the best floatability among three collectors.DFT calculations show that BMBI has the highest occupied molecular orbital(HOMO)energy and strongest collecting effciency.The adsorption mode of three collectors on mineral surface by MD method indicates that the combination processes of collectors with mineral are exothermic,and the higher the binding energy,the frmer the collector adsorbs on the mineral surface and the higher collecting capacity.The calculation results demonstrate that the floatability of three collectors follows the order:BMBI>PMBI>EMBI,which is highly consistent with the flotation tests. Three 2-mercaptobenzimidazole derivatives, 1-ethyl-2-mercapto-benzimidazole (EMBI), 1-propyl- 2-mercapto- benzimidazole (PMBI) and 1-benze-2-mercapto- benzimidazole (BMBI), were designed and synthesized in the paper, and their collecting behavior in flotation separation process of galena over pyrite was investigated by flotation tests on lab scale. Part from this, density functional theory (DFT) calculation and molecular dynamics (MD) simulation were also used to elucidate their collecting mechanism . Results of flotation tests indicate that separation of galena over pyrite is feasible at pH 10, and BMBI has the best floatability among three collectors. DFT calculations show that BMBI has the highest committed molecular orbital (HOMO) energy and strongest collecting effciency. mode of three collectors on mineral surface by MD method indicates that the combination processes of collectors with mineral are exothermic, and the higher the binding energy, the frmer the collector adsorbs on the mineral surface and the higher collecting capacity. the calculation results demonstrate that the floatability of three collectors follows the order: BMBI> PMBI> EMBI, which is highly consistent with the flotation tests.