The micro-structure of an iron-nano particle model and the embedded Sutton-Chen block was studied and simulated using the molecular dynamics method (MD). The spherical iron - nano particle models with the number of atoms respectively at 2000 particles, 3000 particles, 4000 particles and 5000 particles was examined at 300 degrees K in the aperiodic boundary condition. The iron block model with 300 particles was also examined at 300 degrees K in the periodic boundary condition. Features of the structure were analyzed to determine radial distribution function, density, distribution of coordination number. The results showed that the number of particles influences the microstructure of the model in the way that models with different number of particles will have different features in their core structure and surface structure.