In this study the effect of iron on mechanical activation (MA), structural evolution and reduction behavior of hematite (H) and graphite (G) mixture has been investigated. Different amounts of iron (0-10 wt%) were added to the H - G (C/O =1) powder mixture. Then mechanical milling in an inert atmosphere was performed on H - G - Fe mixtures for different time periods (0-50 hr), using a planetary ball mill. X-ray diffraction (XRD) analysis revealed that G peaks completely disappeared in diffraction patterns of samples milled for more than 5 hr, due to the annihilation of G crystal structure. In addition, magnetite (M) peaks emerged in diffraction patterns of samples milled for 10 hr and more, indicating the reduction of some of the H to M due to milling in the presence of G. Obtained results regarding the grain size and structural microstrain of H particles by using one of the methods based on integral breadth analysis (Gaussian-Gaussian approach) showed that milling has a tremendous impact on reducing the grain size and increasing the structural microstrain of H particles and iron enormously intensifies the changes. Furthermore, it was found that H and G amorphization degree and H dislocation density increased by extending the milling time and increasing the iron content. The MA parameters ?/tan? and ?/d were introduced for evaluation of MA and also as criterion for comparing the intensity of MA in different mixtures. The obtained results from the methods were in agreement with previous findings regarding the effect of milling time and iron content on intensity of MA and stored energy in the mixtures. Scanning electron microscopy (SEM) observations revealed that MA produces a compacted composite structure of particles (especially in samples milled for more than 5 hr). The formation mechanism of the aforesaid structure is by getting stuck of H and G brittle particles in iron ductile particles. This state leads to a considerable increase in stored energy. Therefore, iron not only intensifies the structural evolution of H-G mixture but also accelerates taking place of different stages of MA. The effect of milling time and iron content on reduction process of different samples was thoroughly investigated by STA. Samples were heated in an argon atmosphere with a constant heating rate of 10 °C/min from room temperature to 1200 °C. TGL and DTA curves of different samples illustrated that by increasing the milling time and iron content and as a result of higher stored energy in the mixture, the initial temperature of all the reduction reactions notably reduces, while degree of reduction increases. Additionally, RTG and DSC curves showed that reduction rate increases and necessary heat for reduction reactions decreases as milling time and iron content increases. Catalytic effect of iron on reduction process was observed.