Different solution treatments and aging treatments were carried out for GH864 superalloy. The change rule of g ￠ phase content and re-dissolution and precipitation rule of carbides were studied, as well as their effects on grain size, tensile property, creep property and crack growth behavior. Results indicate that by the same heat treatment schedule, the smaller and more uniform the grain sizes are, the higher the strength is; the larger the grain sizes are, the lower the crack growth rate is. In the temperature range of 960-1080 oC, g ￠ phase content decreases with increasing of the solution temperature, but the total amount of g ￠ phases is equal after dual aging treatment. But the cooling medium has no significant influence on the g ￠ content. Because of the interaction between g ￠ phase and carbides, the grain grows slowly below 1020 oC. Besides, the grain size has an obvious effect on the creep property and there is an optimum grain size to obtain the best performance.