Abstract:The hematite precipitation residue in zinc hydrometallurgical process, which could be prepared to high added value iron oxide red by high temperature hydrothermal reaction. In order to reveal the behavior characteristics of iron oxide, basic ferric sulfate and jarosite in high temperature hydrothermal transformation process, the thermal stability of various substances in high temperature hydrothermal reaction were studied through the thermodynamic calculation and experiment. The results showed that the thermal stability of jarosite and basic ferric sulfate is poor, while that of ferric oxide is strong at the temperature of 180~260℃. The high temperature hydrothermal conditions were favorable for the decomposition of jarosite, the hydrolysis of Fe3+ to Fe2O3, and the transformation of basic ferric sulfate to ferric oxide. After the high temperature hydrothermal reaction at 220℃, the iron content increased to 66.83%, in which 97.79% of the iron was ferric oxide and the content of ferric oxide reached 93.36%. However, 0.79% of the S still existed in the form of basic ferric sulfate, 0.18% of the zinc and less than 0.002% of the potassium and sodium existed in the form of physical inclusion.