For improving the acid dissolution process of pyrite cinder, and enhancing the extraction efficiency of Fe, in the condition when the reaction temperature, reaction time and acid over dose coefficient were 70℃, 3 h and 1.2 respectively, the acid dissolution properties of ferric oxide in pyrite cinder were explored under different mass fraction of hydrochloric acid, sulfuric acid and mixed acid. By analyzing the numerical simulation results, it is indicated that the effect of hydrochloric acid is better than that of sulfuric acid. By the mixed acid assay, it is shown the iron dissolution rate of mixed acid is superior to that of single acid with the same concentration. Moreover, for an accurate description of the effect of acid-solubility, the residues after acid dissoltion were analyzed by ICP-OES, XRD and SEM. The results show that the content of Fe₃O₄ in pyrite cinder reduces significantly. The complex structures are degraded into small particles. And after dissolving by sulfuric acid, the metallic elements in pyrite cinder will form new crystals by combining SO₄^2- ion, then impeding the dissolution of iron.