The deformation behavior of GH690 alloy from 298 K to 623 K was investigated by tensile tests. The deformation microstructure was observed by OM, SEM, and TEM. The results show that the twinning is the main deformation mechanism for GH690 alloy at 298 K. Under this condition, both high tensile strength and elongation can be obtained because the deformation twins formed in plastic deformation can act as obstacles to dislocations, resulting in obvious work hardening effect. However, as the number of the deformation twins decreases with increasing of the testing temperature, the deformation mechanism of the alloy translates from twinning to dislocation slipping. As the work hardening effect of dislocation slip mechanism is less than that of twinning mechanism, the tensile strength and plasticity of the alloy are decreased with increasing of the testing temperature.