Abstract: A nickel-based single crystal superalloy was casted using the directional solidification furnace. The long term aging of the alloy was performed at 980 ℃, 1 070 ℃, 1 100 ℃ and 1 140 ℃ for 500 h, respectively. The microstructure and tensile properties at 1 100 ℃ of the alloy after long term aging at different temperature were investigated. The results show that the γ′ phase directional coarsening or rafting and the γ matrix channel widen can be observed in the alloy after long term aging. The coarsening extent of γ′ phases increased and the volume fraction of γ′ phase decreased and space of γ matrix channel obviously increased with rise of aging temperature. No TCP phase was found in the alloy after aging at 980 ℃ for 500 h. The needle shaped TCP phase precipitated after long term aging at 1 070 ℃, 1 100 ℃ and 1 140 ℃ for 500 h. The volume fraction of TCP phase increased with rise of aging temperature. With rise of aging temperature, the yield strength and ultimate tensile strength all decreased with rise of aging temperature, while the elongation increased at first and decreased afterward when aging at 1 140 ℃.