The activity and stability of adsorbed isoamyl xanthate (IX) on a malachite surface before and after sulfidization were studied by calculating the malachite dissolved component and adsorption energy and performing experiments pertaining to the zeta potential, adsorption and desorption experiments, and flotation experiments. In the malachite slurry solution, the main components of copper are Cu2+, CuCO3, HCuO2-, CuO2-, and Cu(CO3)22-, and the concentration distribution of these components is related to the slurry pH value. Between pH 5 to 9, the main copper component in the slurry is CuCO3. The malachite surface is negatively charged; however, the sulfur ions or hydrosulfide ions can still adsorb on the surface at a pH of more than 8.2, which indicates that the sulfidization of malachite corresponds to the chemical adsorption, and the surface electrical properties of the malachite are not obvious to the sulfidization. The adsorption activity of malachite on IX is stronger than that of the sulfide malachite; however, the desorption ratio of IX with respect to the malachite is higher than that pertaining to the sulfide malachite. The adsorption energy of IX on the malachite and sulfide malachite surface was -449.6 kJ/mol and -1134.7 kJ/mol, respectively, and the IX adsorbed on the sulfide malachite surface was more stable. The flotation experiments indicated that the sulfidization of malachite reduced the consumption of IX; however, the recovery of malachite was improved.