Abstract: The reaction mechanism of low-grade limonite powder in the process of heating with different carbon-oxygen ratio was revealed by thermal analysis at temperature of 20 ~1 100 ℃,using coke quenching ash as a new reducing agent.The effects of different carbon ratios on the reaction rate were studied.The experimental results showed that proper excess carbon accelerates the redox.The reaction system was carried out in the two-step reaction mechanism of solid-solid reaction and gas-solid reaction during the heating process,the speed of carbon gasification is very sensitive to temperature,and is the controlling link of the whole reduction reaction.And 635.2 ℃ is the initial carbon reduction temperature,while the temperature is higher than 919.5 ℃,the reduction of iron oxide mainly by direct reduction of CO.After the end of the experiment,the reduction products with carbon-oxygen ratio of 1.2 was analyzed by scanning electron microscopy（SEM）,and It was found that the iron of the reduction product was evenly dispersed,and the iron slag phase boundary was distinct.Through X-ray diffraction（XRD）,it was found that no iron oxide diffraction peak was found in the reduction products,and the iron metal diffraction peak was obviously.