The cyclic stress responses behaviours and failure modes in the low cyclic fatigue of a nickel-based single crystal superalloys DD11 with [0 0 1] orientation at 980℃ and strain amplitude range of 0.5~1.2% have been investigated. The relationship between deformation microstructure and fatigue behaviours was established. The results showed that cyclic softening occurred and the softening degree decreased with increasing strain amplitude. The coarsening of γ" and the broadening of transverse channels of γ caused the movement of dislocation in the γ channel easily, and cyclic softening was resulted. Moreover, the dislocation recovery occurred at the low strain amplitude which also caused cyclic softening. Since the pilling-up of dislocation at the γ/γ" interfaces occurred as the degree of coarsen of γ" and broaden of transverse channels of γ decreased when the strain amplitude was large than 0.8%, resulting in decreasing in the degree of cyclic softening. The fatigue failure mode changed from normal fracture to shear fracture corresponding to a transferring of the crack stable propagation to the instant fracture. Our result is helpful for building the relationship of various blade fatigue failure modes, cyclic stress response and microstructure deformation under different strain amplitudes. It was benefited for the blade design and the strain amplitude allowable range.