During the flotation desilication of iron concentrate, the unavoidable cations (Ca2+, Fe3+) in the pulp have important influences on the floatability of quartz using the anion collecter, and it is of great significance to find out the activation mechanism of the unavoidable cations on the quartz and other pulsar minerals to solve the technical problem of desilication of ultra-pure iron concentrate. At present, there are many pieces of research on the adsorption structure of quartz for collectors, while there are few pieces of research on the adsorption structure and the occurrence mechanism of adsorption strength for inevitable ion-activated quartz. So infrared spectroscopy and XPS analysis were adopted, the spectral characterization of unavoidable ions (Ca2+, Fe3+) activated quartz were performed, and the occurrence forms of oxygen-containing functional groups and unavoidable ions in quartz were analyzed, the mechanism of unavoidable ions activated quartz were also analyzed. The results show that in the infrared characterization, at the appropriate pH value, the addition of Ca2+ and Fe3+ activates the flotation of quartz. When quartz is activated by Ca2+ and Fe3+ and reacts with SDS, the chemical adsorption and physical absorption occur almost at the same time. And the red-shifted wave numbers of Si-O characteristic peak under Fe3+ activation is stronger than that of Ca2+ activation. Ca2+ can activate quartz is due to mono- silicon bond, and the bond action has small bond energy and weak adsorption; Fe3+ activated quartz is due to a dioxy-silicon bond, which has large bond energy and strong adsorption. The XPS test results show that the binding energy of Fe3+ activator activated quartz (Fe(2p) binding energy of 711.16 eV) is stronger than that of Ca2+ activated quartz (Ca(2p) binding energy of 346.93 eV), which makes the chemical displacement of Si(2s) and Si(2p) binding energy larger. It is indicated that the stable Fe-based six-membered ring chelate is formed on the surface of quartz under the activation of Fe3+, and chemical adsorption is more stable and dense, and two active sites are generated; while the unstable Ca-based s chain-like complex is formed on the surface of quartz under the activation of Ca2+, and chemical adsorption is unstable and not so dense. Comprehensive infrared spectrum and XPS analysis show that Fe3+ has stronger activation than Ca2+, and enhance the chemical and physical adsorption between the agent and quartz surface, which is more conducive to the flotation of activation quartz.