The flotation separation of argentite from sphalerite using ammonium dibutyl dithiophosphate (ADD) was studied. Molecular simulation (MS) calculation shows that ADD is chemisorbed on argentite and sphalerite surface in the form of S—P bond. The ADD adsorption on argentite and sphalerite surface in Ag⁺ system was revealed by ICP, Zeta potential and XPS analyses. It is shown that the dissolved Ag⁺ from argentite surface can be absorbed on sphalerite surface in the form of silver hydroxide, and AgOH hydrophilic colloid prevents the adsorption of ADD on sphalerite surface. The ADD adsorption on argentite and sphalerite surface in the pulp containing silver and zinc ions was revealed by adsorption capacity and surface wettability analyses. It is shown that the combined Zn(OH)₂ and AgOH hydrophilic colloid leads to greater ADD adsorption capacity on argentite surface and stronger surface hydrophobicity than sphalerite. Flotation tests demonstrate that ADD enables efficient separation of argentite from sphalerite in the pulp containing silver and zinc ions.