Abstract: The evolution laws and mechanisms of microstructure and mechanical properties of Fe-Ni-based superalloys were studied by different aging processes. The microstructure of the alloy was characterized by optical microscopy (OM), scanning electron microscopy(SEM), transmission electron microscopy(TEM), etc. Mechanical properties of the test alloy were measured and assessed on a tensile testing machine. The experimental results show that after solution treatment at 1050 ℃ and aging treatment at 600 ℃-750 ℃ for 8 h, the microstructure of the Fe-Ni-based superalloy mainly consists of polygonal austenite, containing a small amount of twins and uniformly dispersed precipitates. The nano-sized precipitates are mainly Ni₃Al and Ni₃Ti, and there are also granular TiC and Cr-rich carbides distribute along austenite grain boundaries. When the alloy is aged at 700 ℃, a large number of fine precipitates are dispersed near the grain boundaries, hindering grain boundary migration. So the material exhibits the minimum grain size under this aging condition. When the aging temperature is increased to 750 ℃, the precipitates coarsen and the grain size increases. Yield strength and tensile strength show a trend of increasing first and then decreasing with the rise of aging temperature. After aging at 700 ℃ for 8 h, the alloy has the finest austenite grains and the best comprehensive mechanical properties, among which the yield strength is 683 MPa, the tensile strength is 1083 MPa, and the elongation is 31.6%.