A new wrought Ni-Fe based superalloy was designed for advanced ultra-supercritical boiler tubes beyond 700°C. In this study, the recrystallization treatment of the alloy following cold rolling and the microstructural evolution following 500h, 1000h and 3000h at 750°C were studied. The optimization of heat treatment was performed by thermodynamic calculation and the optimum combination was determined, i.e. annealing treatment at 1150°C for 45min, followed by a two-step aging treatment, at 810°C for 1h and at 770°C for 16h. Following this process, the M(C,N) precipitates and Cr-rich M23C6 carbides were formed at grain boundaries. Following 3000h thermal exposure at 750°C, the coarsening rate of the spherical γʹ precipitates was consistent with the LSW model and similar to that of the IN 740H alloy, while the variation in hardness values was relatively low, as the exposure time was increased. The α-Cr phase was observed after 1000h at 750°C and during the long term thermal exposure the coarsening of α-Cr phase occurred. The formation of α-Cr phase enhanced the intragranular yield strength and hardness values at room temperature and the stability of the mechanical properties was partially improved.