In order to investigate further the effects of void defect on the plastic deformation behavior of α-Fe under tensile load, the molecular dynamic models of the α-Fe samples with the void defects are established and related simulations under uniaxial tension are carried out for a series of models in the void radius of 0 nm, 0.25 nm, 0.50 nm, 0.75 nm and 1.00 nm, respectively. The engineering stress-strain curve and the variations of crystal structure types and defects of each sample with tensile strain are obtained. The results show that overall, the deterioration of tensile mechanical properties of the sample with void is positively related to the void size. The larger the void size is, the easier it is for the sample to enter the plastic deformation stage. Overall, Young's modulus, yield stress, ultimate tensile strength and tensile elongation of the samples containing void decrease with increasing of the radius of the void. The plastic deformation mechanism is of a mixture of the tensile stress-induced structural phase transition and the dislocation slip. However, the characteristics of stress-strain curves change significantly with increasing of the radius of the void, and the plastic yield stage and strain hardening stage of the sample become shorter, the strain hardening stage even vanishes. The research deepens the understandings of the effects of void defect on the plastic deformation mechanism of metals and lay a useful foundation for the subsequent analysis of the physical and mechanical properties of polycrystalline α-Fe materials.