The grain topology was investigated by the topological data from serial sectioning experiment on pure iron and simulation of grain growth with Monte Carlo method. The results show that the mean number of faces of pure iron =12.46 is different from other experimental data in literatures, such as β-brass, Al-Sn alloy, β-titanium, austenite grains of steel, etc. The reason is likely due to the variable surface tension and mobility, which are assumed to play an important role in the evolution of polycrystalline grain systems and thus exert influence on the topological characteristics of the grain network. For the distribution of the number of faces per grain and the grain size distribution, the data from Monte Carlo simulation is consistent with the data from pure iron, but different with the data from Al98Sn2 due to the segregation of Sn atoms to the grain boundary that possibly alter the grain growth process.