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In this study, MD simulations have been performed to observe the behavior of a grain boundary in an alpha -Fe plate under 2-dimensional loading. In MD simulation, the acceleration of every molecule can be achieved from the potential energy and the force interacting between each molecule, and the integration of the motion equation by using Verlet method gives the displacement of each molecule. Initially, four α-Fe rectangular plates having different misorientation angles of grain boundary were modeled by using the Johnson potential and Morse potential. We compared the potential energy of the grain boundary system with that of the perfect structure model. Also, we could obtain the width of the grain boundary by investigating the local potential energy distribution. The tensile loading for each grain boundary models was applied and the behavior of grain boundary was studied. From this study it was clarified that in the case using Johnson potential, the obvious fracture mechanism occurs along the grain boundary, in the case of Morse potential, the diffusion of the grain boundary appears instead of the grain boundary fracture.