Heterogeneous oxidation of gas-phase Hg0 by nano-Fe2O3 was investigated on a fixed bed reactor, and the effects of oxygen concentration, bed temperature, water vapour concentration and particle size have been discussed. The results showed that Hg0 could be oxidized by active oxygen atom on the surface of nano-Fe2O3 as well as lattice oxygen in nano-Fe2O3. Among the factors that affect Hg0 oxidation by nano-Fe2O3, bed temperature plays an important role. More than 40% of total mercury was oxidized at 300°C,however, the test temperature at 400°C could cause sintering of nano-catalyst, which led to a lower efficiency of Hg0 oxidation. The increase of oxygen concentration could promote mercury oxidation and led to higher Hg0 oxidation efficiency. No obvious mercury oxidation was detected in the pure N2 atmosphere, which indicates that oxygen is required in the gas stream for mercury oxidation. The presence of water vapour showed different effects on mercury oxidation depending on its concentration. The lower content of water vapour could promote mercury oxidation, while the higher content of water vapour inhibits mercury oxidation.