The microstructures evolution of a new type Ni-base superalloy used as a component of gas turbine engine has been investigated after long-term aging at 750°C for 2000h. The results indicate that TCP, a harmful phase greatly affects the mechanical properties of the alloy, is un-precipitated in the aging process. phase is precipitated in two kinds of sizes during long-term aging. The shape of larger one is transit from spherical to cubic with prolonging of aging time. The M 23 C 6 carbide formed mainly by Cr, and other elements such as Al, Ti, Co and Mo is also precipitated in both γ matrix and grain boundaries, and the quantities of the carbide increase gradually with the increasing of aging time.