Abstract: Effects of solid solution temperature on the microstructure and tensile properties of a AlCoCrFeNi single-crystal high-entropy superalloy were studied. The results show that there are obvious solidification segregation in the as-cast microstructure of the alloy, and a large amount of γ-γ' eutectic structure exists in the interdendritic region. The solidus and liquidus temperatures of the alloy are determined to be 1353 ℃ and 1380 ℃ by differential thermal analysis, and three multi-stage solid solution treatments are designed based on the DSC results. After solid solution heat treatment, the distribution of solute elements in the alloy becomes more uniform, the dendrite morphology gradually disappears, and the dendrite segregation is improved. The γ' phase in the dendrite trunk and interdendritic region become more dense, the size and difference become smaller, and more uniform. Moreover, as the solid solution temperature increases, the cubicity of the γ' phase significantly increases, the content of eutectic structure in the alloy gradually decreases, and the eutectic size also decreases, but the porosity of the alloy increases. It is also found that as the solid solution temperature increases, the yield strength and tensile strength of the alloy both increase first and then decrease. 1340 ℃ is the optimal solid solution temperature for the alloy, and the microstructure and properties of the alloy under this solid solution temperature are superior to the other two heat treatments