Abstract: According to the service conditions and structural characteristics of nickel-base single crystal super-alloy, the trend of directional coarsening of γ'-grains under the load in the [111] orientation was systematically studied experimentally. The results showed that no trend of any directional coarsening of γ'-grains occurs but they are just growing isotropically by capillarity. FEM calculation showed that the applied stress makes the stress distribution in various matrix channels strongly anisotropic. However, all the channels extended in coarsening process are those where the Von Mises stress is high, while all the channels narrowed gradually are those where the Von Mises stress is low. Such results illustrated that the plastic deformation and its non-uniform distribution play a significant role.