The deformation process of the crack in α-Fe has been simulated under uniaxial tensile deformation by molecular dynamics (MD) method. The effect of crystal orientations on the deformation mechanisms of the crack has been investigated. Various deformation evidences are clearly observed, such as dislocation nucleation and emission, dislocation movement，stacking faults formation or twinning， and formation and coalescence of voids. The simulated results indicate that the crack propagate by a combination of plastic and elastic processes in which the plastic portion of the crack results from the shear behavior of atoms created by the dislocations that are emitted from the crack tip, and the elastic process occurs as a result of the bond-breaking of the atoms in the dislocation-free zone. It has also been studied the deformation and fracture characteristics of the crack in α-Fe and their dependence on the stress state and the temperature.