Molecular dynamics simulation is a computer-based simulation technique that makes it possible to represent the interactions between molecules and atoms over a period of time. This method is based on the equations of Newton's laws and the laws of classical mechanics. In this study, the Fe atom used is Fe which has a BCC crystal structure. The structure of Fe atoms is arranged in layers with a distance between the surfaces of 2.5 , with surface variations of Fe (001) - Fe (001) and Fe (001) - Fe (111). Simulation test results on the crystal structure of Fe with a surface of Fe (001) – Fe (001), at a temperature of 1670K and a temperature of 1973K seen from the slope of the MSD graph that the test results do not have a diffusion coefficient value, on the crystal structure of Fe with a Fe surface ( 001) – Fe (111), at temperatures 1670K, 1973K and 2173K. In the simulation results, it is known that the temperature below the melting point of Fe metal does not occur diffusion process. The higher the temperature used, the greater the value of the diffusion coefficient obtained.