Abstract: Sulfide-amine flotation mechanism of hemimorphite with high content of silicon was studied by solution chemistry theory and first principle calculation. Results show that the flotation recovery of hemimorphite by using long carbon chain amine is higher than that with short carbon chain amine, and the straight-chain amine is better than that of branched one. Satisfactory separation can be obtained when pulp pH is around 11, and the optimal dosage of octadecylamine is about 1.25×10^-4 mol/L. Sodium sulfide can significantly increase the recovery of hemimorphite. Solution chemical analysis shows that the HS^- is the active ingredient of hemimorphite surface activation, and the recovery of hemimorphite can reach greater than 85% when the concentration of HS^- is from 1.950×10^-3 mol/L to 6.180×10^-3 mol/L. First principle calculation shows that HS^- can weakly bond with the Zn and O₁ atoms at hemimorphite surface, and the adsorption of octadecylamine at hemimorphite surface is weaker than that of HS^- ions.