Abstract: An investigation was conducted on the creep behavior and microstructure of a Ni base single crystal superalloy with [001] orientation during creep deformation.The results show that the test samples exhibited a lower steady creep rate and a longer creep life under the higher temperature and stress level.Under the condition of 700℃ and 720MPa TEM observations indicate that $\frac{1}{2}<110> dislocations move in the matrix and react to form the Shockley segments of $\frac{1}{3}<112> dislocations,which cut into the γ' phase and form stacking faults in the precipitates.Under the condition of 900 ℃ and 450MPa,the primary creep stage does not appear.The morphological evaluation of the γ' phase develops from original cubic to raft microstructure.Multiple slip operates and dislocations shearing the γ' phase is the main deformation mechanism during the creep acceleration stage.Under the condition of 1070 ℃ and 150MPa,it is found that the γ' phase gradually changes into raft microstructure,hexagonal dislocation networks appear on the γ/γ' interface,and the regular and dense dislocation networks can inhibit dislocations cutting into the γ' phase and enhance the creep resistance.In the later creep stage,the main deformation characteristic is that the γ' phase is sheared by dislocation pairs.