Abstract: The precipitate behavior and its effect on the mechanical properties of precipitated phase in GH3128 superalloy were studied. The results show that uniform solid solution is obtained at 1200 ℃, resulting in the highest strength and plasticity of GH3128 alloy. The carbides and μ phase are the main precipitates in the service process below 1200 ℃, and the carbides precipitate along the grain boundary. With the increase of service temperature, the range of precipitated carbides increases, the content and the size of carbides also increase. However, the tensile strength and plasticity decrease with increasing insulation temperature. After 900 ℃ thermal insulation treatment, the size and content of the carbide also increase slightly with increasing insulation time. During the long period of thermal insulation, a small amount of μ phase can be separated inside the grain, and the plastic deformation ability greatly reduces.