The microstructural evolution of GH864 superalloy during the hot working process of gas turbine blades was systematically studied by observation of grain size, SEM micrographs and X-ray analysis of samples extracted from rolled bars and forged blades with or without standard heat treatment. The results show that the original rolled bar had uniform equiaxed grains, while necklace structure was found in some locations of blades. This kind of non-uniform grain size was caused mainly by different dynamic recrystallization behavior due to unequal strain in different locations of the blade during forging. Static recrystallization and grain growth happened during heat treatment, which led to more uniform and bigger grain structure. M23C6 and partial secondary MC dissolved after forging. Only a small amount of TiC existed in alloy, which mostly distributed in the grain boundaries, and heat treatment resulted in sufficient precipitation of block-shaped M23C6 discontinuously precipitated along the grain boundaries