Abstract: The tensile creep tests were conducted on a Ni-base single crystal superalloy with 110 orientation under the conditions of 1 040 ℃/150 MPa and 850 ℃/500 MPa,respectively.The creep properties and the microstructure evolution during the creep process were investigated.The longitudinal section morphology of the tensile fracture was observed by SEM.The results show that the γ′ phase of the Ni-base single crystal superalloy with 110 orientation formed the lamellar-type raft structure with inclined 45° with the stress axis under the condition of 1 040 ℃/150 MPa.There was evident difference in the degree of γ′ phase coarsening at different distances away from the fractured surface.However,the γ′ phase was not coarsened obviously under the condition of 850 ℃/500 MPa.