The requirement of meeting rapidly growing demand for energy while maintaining environmentally friendly has been motivating the hot research on thermonuclear fusion. One of the key issues in future fusion reactors is that structural materials, especially fusion device first wall material, will suffer from He cumulative effects and atomic displacements from radiation cascades. Such harsh service conditions lead to the formation of He bubbles, which are responsible for severe degradation of the structural materials (e.g., swelling, embrittlement, loss of ductility etc.). It is thus essential to further understand the formation of He bubbles and hardening characteristics for the development of future nuclear materials. In this work, the behaviors of He segregation and tensile deformation have been investigated by molecular dynamics (MD) simulations in α-Fe with and without dislocations (dislocation densities are 0 and 3.36×10¹¹ cm^-2, respectively ) and at the annealing temperatures of 300 and 600 K with 0.1%He (atomic fraction) injection. The results show that during the process of 300 K annealing, the effect of dislocation is rather weak, and He atoms are easier to form small He clusters by self-trapping. The size of He clusters and the number of dislocation loops are lower. Furthermore, higher temperature can notably intensify He diffusion, and the size of He clusters and the number of dislocation loops both increase at 600 K. In the process of tensile deformation, dislocations can notably accelerate small He clusters to develop into larger He bubbles, which leads to lower yield stress and strain. In addition, at 300 K, the model mainly occurs to brittle fracture and the dislocations density is lower. At 600 K, larger He bubble can promote dislocation multiply and enhance the deformability. Therefore, there exhibits a better plasticity in the model.