Abstract: In order to optimize the Re content in single crystal superalloy, 3%Re and 5%Re nickel-based single crystal super alloys were prepared in a vacuum directional solidification furnace. After heat treatment, they were exposed to 980 ℃ for 400 h, 800 h, and 2 000 h.Besides, their tensile properties were tested when heated to 1 100 ℃.Phase diagrams of the alloys with different Re content were calculated by JMatPro software. The effects of Re contents on dendrite structure, heat treatment structure, heat treatment microstructure and their microstructure changes at different heating temperature and for different duration were investigated by optical microscope(OM), scanning electron microscope (SEM), and energy dispersive spectrometer(EDS). The results show that as the Re content in the single crystal superalloy increases, the primary dendrite spacing decreases slightly while the volume fraction of the eutectic increases.When the size of the γ′phase decreases, the degree of cubic increase. There is no precipitation of TCP phase in two alloys with different Re content after 800 hours′ heating; after heating for 2 000 h, TCP phase precipitated, and its volume fraction increased with the increase of Re content. It can also be concluded that with the increase of Re content, the stability of alloy structure decreases while the tensile properties of the alloy at high temperature significantly increase.