In order to study the high-temperature tensile properties of GH3039 superalloy treated by laser shock peening (LSP), the GH3039 superalloy samples are first peened by a high-energy laser beam. Then, the relaxation behavior of residual stress on the surface of LSP GH3039 after exposure at 600 ℃ for different time, the change in grain size of LSP GH3039 after exposure at 600 ℃ for 5 h, and the high-temperature tensile properties and fractures of GH3039 before and after LSP are compared and analyzed. The results show that after LSP impact, the grains in the near surface of GH3039 are significantly refined, and the residual compressive stress is found in the surface layer of the impact area at a depth of around 1.7 mm. After exposure at 600 ℃ for 5 h, the average grain size of LSP GH3039 increases from 20.5 μm to 28.8 μm, much smaller than the average grain size (47.9 μm) of the base metal. With the increase of exposure time, the relaxation rate of the surface residual stress of LSP GH3039 decreases, which shows a continuous decreasing trend. Compared with that of the base metal, the average ultimate tensile strength of the laser treated sample at 600 ℃ increases by 7.9%, which is attributed to grain refinement and residual compressive stress induced by laser impact treatment.