Oxygen fugacity is a parameter that reflects the oxidation state of the mantle, and it is controlled by temperature, pressure, chemical composition of rock, mineral structure and some other factors. The studies of the oxygen fugacity of the upper mantle are mainly focused on the aspects of the magnesium-olivine- magnetite-quartz system, amphibole-bearing peridotite, basalt (melt) and experimental petrology method. It is widely accepted that mantle oxygen fugacity decreases with the increase of the depth. Nevertheless, natural samples and theoretical studies suggest that the oxygen fugacity of asthenosphere is higher than that of the overlying lithosphere mantle, and even that such an inverse gradient may exist for mantle transition zone compared with the upper mantle. The differences between different tectonic environments and different regions with similar tectonic environments indicate the heterogeneity of oxygen fugacity in horizontal direction. The relationship between substances flux of different layers and the variance of oxygen fugacity is one of the focus in future research on oxygen fugacity. The subduction zone is a great natural laboratory for exploration. Meanwhile, oxygen fugacity in turn influences species of volatiles and their circulating fluxes in different reservoirs, such as carbon and sulfur.