In this research, the coarsening behavior of γ′ precipitates and the effects of Ti/Al ratios to tensile properties after long-term aging in GH984G were investigated. It was suggested that the coarsening of sphere γ′ precipitates growed faster with the aging temperature increased from 700℃ to 800℃. The growth kinetics of the γ′ precipitates were explained by Lifshitz-Slyozov-Wagner’s theory of element diffusion controlled growth at 700℃ and 750℃ during long-term aging. However, the coarsening of γ′ precipitates at 800℃ was contrary to Lifshitz-Slyozov-Wagner’s theory. The γ′ precipitates with high Ti/Al growed fast as the aging time less than 3000h, whereas it slowed down as aging time prolonged. Moreover, the coarsening of γ′ precipitates was fast at 800℃, whereas it slowed down as the aging temperature decreased to 700℃. Ti/Al had no effect on the alloy of standard heat treatment and 700 ℃ tensile properties after long time aging. Therefore, the γ′ precipitates of GH984G alloy possessed excellent stability of microstructure at 700℃, and it could control the γ′ precipitates growth further by adjusting Ti/Al ratio.